Associations between source-apportioned PM2.5 and 30-day readmissions in heart failure patients

BACKGROUND

Air pollution exposure is a significant risk factor for morbidity and mortality, especially for those with pre-existing chronic disease. Previous studies highlighted the risks that long-term particulate matter exposure has for readmissions. However, few studies have evaluated source and component specific associations particularly among vulnerable patient populations.

OBJECTIVES

Use electronic health records from 5556 heart failure (HF) patients diagnosed between July 5, 2004 and December 31, 2010 that were part of the EPA CARES resource in conjunction with modeled source-specific fine particulate matter (PM_2.5) to estimate the association between exposure to source and component apportioned PM_2.5 at the time of HF diagnosis and 30-day readmissions.

METHODS

We used zero-inflated mixed effects Poisson models with a random intercept for zip code to model associations while adjusting for age at diagnosis, year of diagnosis, race, sex, smoking status, and neighborhood socioeconomic status. We undertook several sensitivity analyses to explore the impact of geocoding precision and other factors on associations and expressed associations per interquartile range increase in exposures.

RESULTS

We observed associations between 30-day readmissions and an interquartile range increase in gasoline- (16.9% increase; 95% confidence interval = 4.8%, 30.4%) and diesel-derived PM_2.5 (9.9% increase; 95% confidence interval = 1.7%, 18.7%), and the secondary organic carbon component of PM_2.5 (SOC; 20.4% increase; 95% confidence interval = 8.3%, 33.9%). Associations were stable in sensitivity analyses, and most consistently observed among Black study participants, those in lower income areas, and those diagnosed with HF at an earlier age. Concentration-response curves indicated a linear association for diesel and SOC. While there was some non-linearity in the gasoline concentration-response curve, only the linear component was associated with 30-day readmissions.

DISCUSSION

There appear to be source specific associations between PM_2.5 and 30-day readmissions particularly for traffic-related sources, potentially indicating unique toxicity of some sources for readmission risks that should be further explored.

Short-term PM2.5 exposure and early-readmission risk: a retrospective cohort study in North Carolina heart failure patients

BACKGROUND

Short-term changes in ambient fine particulate matter (PM_2.5) increase the risk for unplanned hospital readmissions. However, this association has not been fully evaluated for high-risk patients or examined to determine if the readmission risk differs based on time since discharge. Here we investigate the relation between ambient PM_2.5 and 30-day readmission risk in heart failure (HF) patients using daily time windows and examine how this risk varies with respect to time following discharge.

METHODS

We performed a retrospective cohort study of 17,674 patients with a recorded HF diagnosis between 2004 and 2016. The cohort was identified using the EPA CARES electronic health record resource. The association between ambient daily PM_2.5 (μg/m³) concentration and 30-day readmissions was evaluated using time-dependent Cox proportional hazard models. PM_2.5 associated readmission risk was examined throughout the 30-day readmission period and for early readmissions (1-3 days post-discharge). Models for 30-day readmissions included a parametric continuous function to estimate the daily PM_2.5 associated readmission hazard. Fine-resolution ambient PM_2.5 data were assigned to patient residential address and hazard ratios are expressed per 10 μg/m³ of PM_2.5. Secondary analyses examined potential effect modification based on the time after a HF diagnosis, urbanicity, medication prescription, comorbidities, and type of HF.

RESULTS

The hazard of a PM_2.5-related readmission within 3 days of discharge was 1.33 (95% CI 1.18-1.51). This PM_2.5 readmission hazard was slightly elevated in patients residing in non-urban areas (1.43, 95%CI 1.22-1.67) and for HF patients without a beta-blocker prescription prior to the readmission (1.35; 95% CI 1.19-1.53).

CONCLUSION

Our findings add to the evidence indicating substantial air quality-related health risks in individuals with underlying cardiovascular disease. Hospital readmissions are key metrics for patients and providers alike. As a potentially modifiable risk factor, air pollution-related interventions may be enacted that might assist in reducing costly and burdensome unplanned readmissions.

Associations between short-term exposure to PM2.5 and cardiomyocyte injury in myocardial infarction survivors in North Carolina

Objective

Short-term ambient fine particulate matter (PM_2.5) is associated with adverse cardiovascular events including myocardial infarction (MI). However, few studies have examined associations between PM_2.5 and subclinical cardiomyocyte damage outside of overt cardiovascular events. Here we evaluate the impact of daily PM_2.5 on cardiac troponin I, a cardiomyocyte specific biomarker of cellular damage.

Methods

We conducted a retrospective cohort study of 2924 patients identified using electronic health records from the University of North Carolina Healthcare System who had a recorded MI between 2004 and 2016. Troponin I measurements were available from 2014 to 2016, and were required to be at least 1 week away from a clinically diagnosed MI. Daily ambient PM_2.5 concentrations were estimated at 1 km resolution and assigned to patient residence. Associations between log-transformed troponin I and daily PM_2.5 were evaluated using distributed lag linear mixed effects models adjusted for patient demographics, socioeconomic status and meteorology.

Results

A 10 µg/m³ elevation in PM_2.5 3 days before troponin I measurement was associated with 0.06 ng/mL higher troponin I (95% CI=0.004 to 0.12). In stratified models, this association was strongest in patients that were men, white and living in less urban areas. Similar associations were observed when using 2-day rolling averages and were consistently strongest when using the average exposure over the 5 days prior to troponin I measurement.

Conclusions

Daily elevations in PM_2.5 were associated with damage to cardiomyocytes, outside of the occurrence of an MI. Poor air quality may cause persistent damage to the cardiovascular system leading to increased risk of cardiovascular disease and adverse cardiovascular events.

A cross-sectional study of brownfields and birth defects

BACKGROUND

Brownfields are a multitude of abandoned and disused sites, spanning many former purposes. Brownfields represent a heterogenous yet ubiquitous exposure for many Americans, which may contain hazardous wastes and represent urban blight. Neonates and pregnant individuals are often sensitive to subtle environmental exposures. We evaluate whether residential brownfield exposure is associated with birth defects.

METHODS

Using North Carolina birth records from 2003 to 2015, we sampled 753,195 births with 39,495 defects identified. We examined defect groups and 30 distinct phenotypes. Number of brownfields within 2,000 m of the residential address at birth was summed. We utilized mixed effects multivariable logistic regression models adjusted for demographic and environmental covariates available from birth records, 2010 Census, and EPA's Environmental Quality Index to estimate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

We observed positive associations between cardiovascular and external defect groups (OR [95% CI]: 1.07 [1.02-1.13] and 1.17 [1.01-1.35], respectively) and any brownfield exposure. We also observed positive associations with atrial septal and ventricular septal defects (1.08 [1.01-1.16] and 1.15 [1.03-1.28], respectively), congenital cataracts (1.38 [0.98-1.96]), and an inverse association with gastroschisis (0.74 [0.58-0.94]). Effect estimates for several additional defects were positive, though we observed null associations for most group and individual defects. Additional analyses indicated an exposure-response relationship for several defects across levels of brownfield exposure.

CONCLUSIONS

Our results indicate that residential proximity to brownfields is associated with birth defects, especially cardiovascular and external defects. In-depth analyses of individual defects and specific contaminants or brownfield sites may reveal additional novel associations.

Associations between neighborhood socioeconomic cluster and hypertension, diabetes, myocardial infarction, and coronary artery disease within a cohort of cardiac catheterization patients

Background

Neighborhood-level socioeconomic status (SES) is associated with health outcomes, including cardiovascular disease and diabetes, but these associations are rarely studied across large, diverse populations.

Methods

We used Ward’s Hierarchical clustering to define eight neighborhood clusters across North Carolina using 11 census-based indicators of SES, race, housing, and urbanicity and assigned 6992 cardiac catheterization patients at Duke University Hospital from 2001 to 2010 to clusters. We examined associations between clusters and coronary artery disease index > 23 (CAD), history of myocardial infarction, hypertension, and diabetes using logistic regression adjusted for age, race, sex, body mass index, region of North Carolina, distance to Duke University Hospital, and smoking status.

Results

Four clusters were urban, three rural, and one suburban higher-middle-SES (referent). We observed greater odds of myocardial infarction in all six clusters with lower or middle-SES. Odds of CAD were elevated in the rural cluster that was low-SES and plurality Black (OR 1.16, 95% CI 0.94-1.43) and in the rural cluster that was majority American Indian (OR 1.31, 95% CI 0.91-1.90). Odds of diabetes and hypertension were elevated in two urban and one rural low- and lower-middle SES clusters with large Black populations.

Conclusions

We observed higher prevalence of cardiovascular disease and diabetes in neighborhoods that were predominantly rural, low-SES, and non-White, highlighting the importance of public health and healthcare system outreach into these communities to promote cardiometabolic health and prevent and manage hypertension, diabetes and coronary artery disease.

Evaluation of PM2.5 air pollution sources and cardiovascular health

Long-term air pollution exposure, notably fine particulate matter, is a global contributor to morbidity and mortality and a known risk factor for coronary artery disease (CAD) and myocardial infarctions (MI). Knowledge of impacts related to source-apportioned PM2.5 is limited. New modeling methods allow researchers to estimate source-specific long-term impacts on the prevalence of CAD and MI. The Catheterization Genetics (CATHGEN) cohort consists of patients who underwent a cardiac catheterization at Duke University Medical Center between 2002 and 2010. Severity of coronary blockage was determined by coronary angiography and converted into a binary indicator of clinical CAD. History of MI was extracted from medical records. Annual averages of source specific PM2.5 were estimated using an improved gas-constrained source apportionment model for North Carolina from 2002 to 2010. We tested six sources of PM2.5 mass for associations with CAD and MI using mixed effects multivariable logistic regression with a random intercept for county and multiple adjustments. PM2.5 fractions of ammonium bisulfate and ammonium nitrate were associated with increased prevalence of CAD (odds ratio [OR] 1.20; 95% CI = 1.11, 1.22 and OR 1.18; 95% CI = 1.05, 1.32, respectively). PM2.5 from ammonium bisulfate and ammonium nitrate were also associated with increased prevalence of MI (OR 1.20; 95% CI = 1.10, 1.29 and OR 1.35; 95% CI = 1.20, 1.53, respectively). Greater PM2.5 concentrations of ammonium bisulfate and ammonium nitrate are associated with greater MI and CAD prevalence. The association with bisulfate suggests aerosol acidity may play a role. Our findings suggest analyses of source specific PM2.5 mass can reveal novel associations.

Long-Term Exposure to Particulate Air Pollution Is Associated With 30-Day Readmissions and Hospital Visits Among Patients With Heart Failure

Background

Long‐term air pollution exposure is a significant risk factor for inpatient hospital admissions in the general population. However, we lack information on whether long‐term air pollution exposure is a risk factor for hospital readmissions, particularly in individuals with elevated readmission rates.

Methods and Results

We determined the number of readmissions and total hospital visits (outpatient visits+emergency room visits+inpatient admissions) for 20 920 individuals with heart failure. We used quasi‐Poisson regression models to associate annual average fine particulate matter at the date of heart failure diagnosis with the number of hospital visits and 30‐day readmissions. We used inverse probability weights to balance the distribution of confounders and adjust for the competing risk of death. Models were adjusted for age, race, sex, smoking status, urbanicity, year of diagnosis, short‐term fine particulate matter exposure, comorbid disease, and socioeconomic status. A 1‐µg/m³ increase in fine particulate matter was associated with a 9.31% increase (95% CI, 7.85%–10.8%) in total hospital visits, a 4.35% increase (95% CI, 1.12%–7.68%) in inpatient admissions, and a 14.2% increase (95% CI, 8.41%–20.2%) in 30‐day readmissions. Associations were robust to different modeling approaches.

Conclusions

These results highlight the potential for air pollution to play a role in hospital use, particularly hospital visits and readmissions. Given the elevated frequency of hospitalizations and readmissions among patients with heart failure, these results also represent an important insight into modifiable environmental risk factors that may improve outcomes and reduce hospital use among patients with heart failure.

Waterless Hand Cleansing with Chlorhexidine during the Neonatal Period by Mothers and Other Household Members: Findings from a Randomized Controlled Trial

Observational data suggest maternal handwashing with soap prevents neonatal mortality. We tested the impact of a chlorhexidine-based waterless hand cleansing promotion on the behavior of mothers and other household members. In rural Bangladesh in 2014, we randomized consenting pregnant women to chlorhexidine provision and hand cleansing promotion or standard practices. We compared hand cleansing with chlorhexidine or handwashing with soap before baby care, among mothers and household members in the two groups, and measured chlorhexidine use in the intervention arm. Chlorhexidine was observed in the baby's sleep space in 97% of 130 intervention homes, versus soap in 59% of 128 control homes. Hand cleansing before baby care was observed 5.6 times more frequently among mothers in the intervention arm than in the controls (95% CI = 4.0-7.7). Hand cleansing was significantly more frequently observed in the intervention arm among women other than the mother (RR = 10.9) and girls (RR = 37.0). Men and boys in the intervention arm cleansed hands before 29% and 44% of baby care events, respectively, compared with 0% in the control arm. The median number of grams consumed during the neonatal period was 176 (IQR = 95-305 g), about 7.8 g/day (IQR = 4.2-13.8 g). Promotion of waterless chlorhexidine increased hand cleansing behavior among mothers and other household members. Discrepancy between observed use and measured chlorhexidine consumption suggested courtesy bias in structured observations. A waterless hand cleanser may represent one component of the multimodal strategies to prevent neonatal infections in low-resource settings.

Associations Between Long-Term Fine Particulate Matter Exposure and Mortality in Heart Failure Patients

Background Environmental health risks for individuals with heart failure (HF) have been inadequately studied, as these individuals are not well represented in traditional cohort studies. To address this we studied associations between long-term air pollution exposure and mortality in HF patients. Methods and Results The study population was a hospital-based cohort of individuals diagnosed with HF between July 1, 2004 and December 31, 2016 compiled using electronic health records. Individuals were followed from 1 year after initial diagnosis until death or the end of the observation period (December 31, 2016). We used Cox proportional hazards models to evaluate the association of annual average fine particulate matter (PM_2.5) exposure at the time of initial HF diagnosis with all-cause mortality, adjusted for age, race, sex, distance to the nearest air pollution monitor, and socioeconomic status indicators. Among 23 302 HF patients, a 1 μg/m³ increase in annual average PM_2.5 was associated with an elevated risk of all-cause mortality (hazard ratio 1.13; 95% CI, 1.10-1.15). As compared with people with exposures below the current national PM_2.5 exposure standard (12 μg/m³), those with elevated exposures experienced 0.84 (95% CI, 0.73-0.95) years of life lost over a 5-year period, an observation that persisted even for those residing in areas with PM_2.5 concentrations below current standards. Conclusions Residential exposure to elevated concentrations of PM_2.5 is a significant mortality risk factor for HF patients. Elevated PM_2.5 exposures result in substantial years of life lost even at concentrations below current national standards.

Validation of a Dietary Questionnaire to Screen Omega-3 Fatty Acids Levels in Healthy Adults

To facilitate a clinical observational study to identify healthy volunteers with low (defined as ≤4%) and high (defined as ≥5.5%) omega-3 indices, a dietary questionnaire to rapidly assess habitual dietary intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was developed. This study aimed to determine the validity of this newly developed dietary questionnaire. One hundred and eight volunteers were included and were assessed for habitual dietary intake of EPA and DHA using the questionnaire. The United States Department of Agriculture food products database and nutrition fact label was referenced for calculation. Blood samples were collected for the analysis of fatty acids in whole blood specimens and to derive omega-3 indices. A linear correlation was observed between reported dietary consumption of EPA, DHA, EPA+DHA and the whole blood levels of EPA, DHA, and the omega-3 indices (r = 0.67, 0.62, 0.67, respectively, p < 0.001 for all). The findings also suggested that the questionnaire was substantially better at identifying volunteers with high omega-3 indices (sensitivity 89%, specificity 84%, and agreement 86%) compared to volunteers with low omega-3 indices (sensitivity 100%, specificity 66%, and agreement 42%). In conclusion, this newly developed questionnaire is an efficient tool for the assessment of omega-3 indices in study populations and is particularly effective in identifying individuals with high omega-3 indices.

Long-term exposure to ambient air pollution and renal function in African Americans: the Jackson Heart Study

Renal dysfunction is prevalent in the US among African Americans. Air pollution is associated with renal dysfunction in mostly white American populations, but has not been studied among African Americans. We evaluated cross-sectional associations between 1-year and 3-year fine particulate matter (PM_2.5) and ozone (O₃) concentrations, and renal function among 5090 African American participants in the Jackson Heart Study. We used mixed-effect linear regression to estimate associations between 1-year and 3-year PM_2.5 and O₃ and estimated glomerular filtration rate (eGFR), urine albumin/creatinine ratio (UACR), serum creatinine, and serum cystatin C, adjusting for: sociodemographic factors, health behaviors, and medical history and accounting for clustering by census tract. At baseline, JHS participants had mean age 55.4 years, and 63.8% were female; mean 1-year and 3-year PM_2.5 concentrations were 12.2 and 12.4 µg/m³, and mean 1-year and 3-year O₃ concentrations were 40.2 and 40.7 ppb, respectively. Approximately 6.5% of participants had reduced eGFR (< 60 mL/min/1.73m²) and 12.7% had elevated UACR (> 30 mg/g), both indicating impaired renal function. Annual and 3-year O₃ concentrations were inversely associated with eGFR and positively associated with serum creatinine; annual and 3-year PM_2.5 concentrations were inversely associated with UACR. We observed impaired renal function associated with increased O₃ but not PM_2.5 exposure among African Americans.

Air pollution dispersion from biomass stoves to neighboring homes in Mirpur, Dhaka, Bangladesh

BACKGROUND

Indoor air pollution, including fine particulate matter (PM2.5) and carbon monoxide (CO), is a major risk factor for pneumonia and other respiratory diseases. Biomass-burning cookstoves are major contributors to PM2.5 and CO concentrations. However, high concentrations of PM2.5 (> 1000 μg/m3) have been observed in homes in Dhaka, Bangladesh that do not burn biomass. We described dispersion of PM2.5 and CO from biomass burning into nearby homes in a low-income urban area of Dhaka, Bangladesh.

METHODS

We recruited 10 clusters of homes, each with one biomass-burning (index) home, and 3-4 neighboring homes that used cleaner fuels with no other major sources of PM2.5 or CO. We administered a questionnaire and recorded physical features of all homes. Over 24 h, we recorded PM2.5 and CO concentrations inside each home, near each stove, and outside one neighbor home per cluster. During 8 of these 24 h, we conducted observations for pollutant-generating activities such as cooking. For each monitor, we calculated geometric mean PM2.5 concentrations at 5-6 am (baseline), during biomass burning times, during non-cooking times, and over 24 h. We used linear regressions to describe associations between monitor location and PM2.5 and CO concentrations.

RESULTS

We recruited a total of 44 homes across the 10 clusters. Geometric mean PM2.5 and CO concentrations for all monitors were lowest at baseline and highest during biomass burning. During biomass burning, linear regression showed a decreasing trend of geometric mean PM2.5 and CO concentrations from the biomass stove (326.3 μg/m3, 12.3 ppm), to index home (322.7 μg/m3, 11.2 ppm), neighbor homes sharing a wall with the index home (278.4 μg/m3, 3.6 ppm), outdoors (154.2 μg/m3, 0.7 ppm), then neighbor homes that do not share a wall with the index home (83.1 μg/m3,0.2 ppm) (p = 0.03 for PM2.5, p = 0.006 for CO).

CONCLUSION

Biomass burning in one home can be a source of indoor air pollution for several homes. The impact of biomass burning on PM2.5 or CO is greatest in homes that share a wall with the biomass-burning home. Eliminating biomass burning in one home may improve air quality for several households in a community.

A National County-Level Assessment of U.S. Nursing Facility Characteristics Associated with Long-Term Exposure to Traffic Pollution in Older Adults

Long-term exposure to ambient air pollution increases disease risk in older adults. Nursing facilities located near major roadways potentially expose older adults to traffic pollution. No studies, however, have described the association between nursing facilities and traffic pollution. We obtained data on facility- and census-tract-level characteristics of 15,706 U.S. facilities from the Medicare Nursing Home Compare datasets. We calculated distance to major roadways and traffic density for each facility. In the contiguous U.S. (as of 2014), 345,792 older adults, about 27% of residents in non-hospital facilities, lived within 150 m major roadways (A1 or A2) in 3876 (28% of sampled) facilities. Nationally, for-profit facilities, high-occupancy facilities, and facilities in census tracts with higher percentages of minorities were more likely to have higher exposure to traffic. Counties in Virginia, New York City, and Rhode Island have the highest percent of residents and facilities near major roads. Nationally, over one-quarter of sampled facilities are located near major roadways. Attributes potentially associated with higher exposure to traffic included “for-profit” and “higher minority census tract”. Proximity to major roadways may be an important factor to consider in siting nursing facilities. Our results inform potential intervention strategy at both county and facility level.

Effects of smoke-free air law on acute myocardial infarction hospitalization in Indianapolis and Marion County, Indiana

BACKGROUND

A comprehensive smoke-free air law was enacted on June 1, 2012 in most of Marion County, Indiana, including all of the City of Indianapolis. We evaluated changes in acute myocardial infarction (AMI) admission rates in Indianapolis and Marion County before compared to after the law.

METHODS

We collected AMI admissions from five Marion County hospitals between May 2007 and December 2014. We used Poisson regression to evaluate the overall effects of the law on monthly AMI hospitalizations, adjusting for month, seasonality, meteorology, air pollution, and hospital utilization. We tested the interactions between the law and AMI risk factors on monthly AMI admission rates to identify subpopulations for which the effects might be stronger.

RESULTS

Monthly AMI admissions declined 20% (95% CI 14-25%) in Marion County and 25% (95% CI 20-29%) in Indianapolis after the law was implemented. We observed decreases among never (21%, 95% CI 13-29%), former (28%, 95% CI 21-34%), and current smokers (26%, 95% CI 11-38%); Medicaid beneficiaries (19%, 95% CI 9-29%) and non-beneficiaries (26%, 95% CI 20-31%). We observed decreases among those with a history of diabetes (Yes: 22%, 95% CI 14-29%; No: 25%, 95% CI 18-31%), congestive heart failure (Yes: 23%, 95% CI 16-30%; No: 24%, 95% CI 17-31%), and hypertension (Yes: 23%, 95% CI 17-28%: No: 26%, 95% CI 15-36%).

CONCLUSIONS

We observed decreases in AMI admissions comparable with previous studies. We identified subpopulations who benefitted from the law, such as former and current smokers, and those without comorbidities such as congestive heart failure and hypertension.

Pilot Intervention Study of Household Ventilation and Fine Particulate Matter Concentrations in a Low-Income Urban Area, Dhaka, Bangladesh

Fine particulate matter (PM_2.5) is a risk factor for pneumonia; ventilation may be protective. We tested behavioral and structural ventilation interventions on indoor PM_2.5 in Dhaka, Bangladesh. We recruited 59 good ventilation (window or door in ≥ 3 walls) and 29 poor ventilation (no window, one door) homes. We monitored baseline indoor and outdoor PM_2.5 for 48 hours. We asked all participants to increase ventilation behavior, including opening windows and doors, and operating fans. Where permitted, we installed windows in nine poor ventilation homes, then repeated PM_2.5 monitoring. We estimated effects using linear mixed-effects models and conducted qualitative interviews regarding motivators and barriers to ventilation. Compared with poor ventilation homes, good ventilation homes were larger, their residents wealthier and less likely to use biomass fuel. In multivariable linear mixed-effects models, ventilation structures and opening a door or window were inversely associated with the number of hours PM_2.5 concentrations exceeded 100 and 250 μg/m³. Outdoor air pollution was positively associated with the number of hours PM_2.5 concentrations exceeded 100 and 250 μg/m³. Few homes accepted window installation, due to landlord refusal and fear of theft. Motivators for ventilation behavior included cooling of the home and sunlight; barriers included rain, outdoor odors or noise, theft risk, mosquito entry, and, for fan use, perceptions of wasting electricity or unavailability of electricity. We concluded that ventilation may reduce indoor PM_2.5 concentrations but, there are barriers to increasing ventilation and, in areas with high ambient PM_2.5 concentrations, indoor concentrations may remain above recommended levels.

Residential distance to major roadways and cardiac structure in African Americans: cross-sectional results from the Jackson Heart Study

BACKGROUND

Heart failure (HF) is a significant source of morbidity and mortality among African Americans. Ambient air pollution, including from traffic, is associated with HF, but the mechanisms remain unknown. The objectives of this study were to estimate the cross-sectional associations between residential distance to major roadways with markers of cardiac structure: left ventricular (LV) mass index, LV end-diastolic diameter, LV end-systolic diameter, and LV hypertrophy among African Americans.

METHODS

We studied baseline participants of the Jackson Heart Study (recruited 2000-2004), a prospective cohort of cardiovascular disease (CVD) among African Americans living in Jackson, Mississippi, USA. All cardiac measures were assessed from echocardiograms. We assessed the associations between residential distance to roads and cardiac structure indicators using multivariable linear regression or multivariable logistic regression, adjusting for potential confounders.

RESULTS

Among 4826 participants, residential distance to road was <150 m for 103 participants, 150-299 m for 158, 300-999 for 1156, and ≥1000 m for 3409. Those who lived <150 m from a major road had mean 1.2 mm (95% CI 0.2, 2.1) greater LV diameter at end-systole compared to those who lived ≥1000 m. We did not observe statistically significant associations between distance to roads and LV mass index, LV end-diastolic diameter, or LV hypertrophy. Results did not materially change after additional adjustment for hypertension and diabetes or exclusion of those with CVD at baseline; results strengthened when modeling distance to A1 roads (such as interstate highways) as the exposure of interest.

CONCLUSIONS

We found that residential distance to roads may be associated with LV end-systolic diameter, a marker of systolic dysfunction, in this cohort of African Americans, suggesting a potential mechanism by which exposure to traffic pollution increases the risk of HF.

Household-level risk factors for secondary influenza-like illness in a rural area of Bangladesh

Objective

To describe household‐level risk factors for secondary influenza‐like illness (ILI), an important public health concern in the low‐income population of Bangladesh.

Methods

Secondary analysis of control participants in a randomised controlled trial evaluating the effect of handwashing to prevent household ILI transmission. We recruited index‐case patients with ILI – fever (<5 years); fever, cough or sore throat (≥5 years) – from health facilities, collected information on household factors and conducted syndromic surveillance among household contacts for 10 days after resolution of index‐case patients’ symptoms. We evaluated the associations between household factors at baseline and secondary ILI among household contacts using negative binomial regression, accounting for clustering by household.

Results

Our sample was 1491 household contacts of 184 index‐case patients. Seventy‐one percentage reported that smoking occurred in their home, 27% shared a latrine with one other household and 36% shared a latrine with >1 other household. A total of 114 household contacts (7.6%) had symptoms of ILI during follow‐up. Smoking in the home (RR_adj 1.9, 95% CI: 1.2, 3.0) and sharing a latrine with one household (RR_adj 2.1, 95% CI: 1.2, 3.6) or >1 household (RR_adj 3.1, 95% CI: 1.8–5.2) were independently associated with increased risk of secondary ILI.

Conclusion

Tobacco use in homes could increase respiratory illness in Bangladesh. The mechanism between use of shared latrines and household ILI transmission is not clear. It is possible that respiratory pathogens could be transmitted through faecal contact or contaminated fomites in shared latrines.

Alcohol intake over the life course and breast cancer survival in Western New York exposures and breast cancer (WEB) study: quantity and intensity of intake

Alcohol intake is a risk factor for breast cancer, but the association between alcohol and mortality among breast cancer survivors is poorly understood. We examined the association between alcohol intake from all sources, assessed by cognitive lifetime drinking history, and all-cause and breast cancer mortality among women with breast cancer (N = 1,097) who participated in a population-based case-control study. Vital status was ascertained through 2006 using the National Death Index. Using Cox proportional hazards models, we computed hazard ratios for all-cause and breast cancer mortality in association with alcohol intake. We examined lifetime volume and intensity (drinks per drinking day) of alcohol consumption as well as drinking status during various life periods. Analyses were stratified by menopausal status. After adjustment for total intake, postmenopausal women with consumption of four or more drinks per drinking day over their lifetimes were nearly three times more likely to die from any cause compared to abstainers (HR 2.94, 95 % CI 1.31, 6.62). There was a similar but non-significant association with breast cancer mortality (HR 2.68, 95 % CI 0.94, 7.67). Postmenopausal women who drank one drink or fewer per drinking day between menarche and first birth had a significantly decreased hazard of all-cause (HR 0.54, 95 % CI 0.31, 0.95) and breast cancer mortality (HR 0.27, 95 % CI 0.09, 0.77). Premenopausal breast cancer survival was not associated with drinking intensity. We observed no associations between drinking status or total volume of alcohol intake and breast cancer or all-cause mortality. High-intensity alcohol consumption may be associated with decreased survival in postmenopausal women with breast cancer. Low-intensity alcohol consumption between menarche and first birth may be inversely associated with all-cause and breast cancer mortality; this period may be critical for development of and survival from breast cancer. Intensity of alcohol intake may be a more important factor than absolute volume of intake on survival in women with breast cancer.

Dietary intakes of total and specific lignans are associated with clinical breast tumor characteristics

Dietary lignans may affect breast cancer by modifying tumor characteristics likely to affect prognosis. We investigated usual dietary intakes of total and specific lignans with tumor characteristics in 683 women with breast cancer and 611 healthy women without breast cancer enrolled in the Data Bank and BioRepository at Roswell Park Cancer Institute (RPCI). Clinicopathologic data were abstracted from the RPCI breast cancer database. Dietary lignan intakes were calculated from FFQ. OR and 95% CI were estimated with logistic regression adjusting for potential confounders and stratified by menopausal status. Women in the highest compared to the lowest tertile of total lignan intakes had a 40-50% lower odds of breast cancer regardless of menopausal status and substantially reduced odds of an invasive tumor, especially among premenopausal women [OR 0.48 (95% CI 0.26-0.86)]. Lignan intakes were inversely associated with odds of grade 3 tumors among premenopausal women. Lignan intakes were inversely associated with risk of estrogen receptor (ER) negative (ER(-)) breast cancer among premenopausal women [OR 0.16 (95% CI 0.03-0.44)] and particularly triple negative tumors [ER(-), progesterone receptor negative, HER2 negative; OR 0.16 (95% CI 0.04-0.62)]. There were significant differences in the contribution to these effects by specific lignans, especially matairesinol and lariciresinol. In summary, in this case-control study of dietary lignan intakes and breast cancer, we found that higher lignan intakes were associated with lower risks of breast cancer with more favorable prognostic characteristics. Future investigations are warranted to explore the strong associations observed with ER(-) cancer in premenopausal women.

Abstract A79: Usual intakes of total and specific isoflavones in association with breast tumor characteristics

Introduction: Although soy isoflavones intakes have been associated with reduced breast cancer risk in many populations, there is still uncertainty as to the relationships between these compounds and breast cancer clinical characteristics, which may have implications for prognosis and survival.

Methods: Included in this study were women with newly diagnosed, incident breast cancer (n = 683) and women without a history of breast cancer (n = 611) enrolled in Roswell Park Cancer Institute's Data Bank and BioRepository. Epidemiologic and dietary data were collected by self-administered questionnaires, and clinical data from breast cancer cases were abstracted from medical records. Total and specific isoflavones intakes were calculated from the food frequency questionnaire using published food composition data. Polytomous logistic regression was performed to determine the relationship between tertiles of intakes of total and specific isoflavones and tumor characteristics, adjusting for known risk factors and stratifying by menopausal status.

Results: In the sample overall, compared to controls, cases in the highest vs. lowest tertile of total isoflavone intake had approximately 30% decreased odds of having an invasive tumor and an approximately 60% decreased odds of having a grade 1 tumor. Among specific isoflavones, intakes in the highest vs. lowest tertile were associated as follows: for genistein, an approximately 60% decreased odds of having grade 1 tumor; and for glycetein, an approximately 25% decreased odds of being a case, 60% decreased odds of having grade1 tumor, and 30% decreased odds of having HER2 negative tumor. In postmenopausal women only, cases in the highest vs. lowest tertile of glycetein intake had an approximately 30% decreased odds of having luminal A or stage I disease. In premenopausal women only, higher total isoflavone, daidzein, genistein, and glycetein intakes were associated with an approximately 70% decreased odds of having a large (&gt;2cm) tumor. Further, those premenopausal women in the highest vs. lowest tertile of total isoflavone and genistein intakes had an approximately 60% decreased odds of having stage II breast cancer. Higher intakes of total and specific isoflavones were not associated with tumor characteristics indicative of a poor prognosis.

Conclusions: In general, higher total isoflavone intake (and some specific isoflavones intakes) were associated with a reduced risk of tumors with more favorable prognostic characteristics. Intakes of total and specific isoflavones had no association with tumors having less favorable characteristics. In premenopausal women, however, higher intakes of isoflavones appear to be associated with a decreased risk of having large (&gt;2cm) tumors. In this study, there is little evidence that isoflavones are associated with indicators associated with poor prognosis or recurrence, suggesting that these compounds may operate through mechanisms specific to the biologic heterogeneity of the tumor. Further research is warranted to address the impact of tumor heterogeneity in studies of isoflavones and breast cancer.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):A79.

Aggressiveness of HNSCC tumors depends on expression levels of cortactin, a gene in the 11q13 amplicon

11q13 amplification is a late-stage event in several cancers that is often associated with poor prognosis. Among 11q13-amplified genes, the actin assembly protein cortactin/CTTN is considered a likely candidate for direct involvement in tumor progression, because of its cell motility-enhancing functions. We modulated cortactin expression in head and neck squamous cell carcinoma (HNSCC) lines. Cortactin expression levels directly correlated with tumor size, vascularization, and cell proliferation in an orthotopic HNSCC in vivo model. In contrast, under normal in vitro culture conditions, cortactin expression levels had no effect on cell proliferation. However, cell lines in which cortactin expression was reduced by knockdown (KD) grew poorly in vitro under harsh conditions of growth-factor deprivation, anchorage independence, and space constraint. Conversely, overexpression of cortactin enhanced in vitro growth under the same harsh conditions. Surprisingly, defects in growth factor-independent proliferation of cortactin-KD cells were rescued by co-culture with cortactin-expressing cells. Since the co-cultured cells are separated by permeable filters, cortactin-expressing cells must secrete growth-supporting autocrine factors to rescue the cortactin-KD cells. Overall, cortactin expression modulates multiple cellular traits that may allow survival in a tumor environment, suggesting that the frequent overexpression of cortactin in tumors is not an epiphenomenon but rather promotes tumor aggressiveness.

Arp2/3 complex: advances on the inner workings of a molecular machine

Several new papers report progress on the structure and function of Arp2/3 complex. A crystal structure, a cryo-EM structure, and a reconstitution of the complex from subunits have been reported. New results also address the nucleation mechanism and the role of bound nucleotide.

Cortactin promotes and stabilizes Arp2/3-induced actin filament network formation

Cortactin is a c-src substrate associated with sites of dynamic actin assembly at the leading edge of migrating cells. We previously showed that cortactin binds to Arp2/3 complex, the essential molecular machine for nucleating actin filament assembly. In this study, we demonstrate that cortactin activates Arp2/3 complex based on direct visualization of filament networks and pyrene actin assays. Strikingly, cortactin potently inhibited the debranching of filament networks. When cortactin was added in combination with the active VCA fragment of N-WASp, they synergistically enhanced Arp2/3-induced actin filament branching. The N-terminal acidic and F-actin binding domains of cortactin were both necessary to activate Arp2/3 complex. These results support a model in which cortactin modulates actin filament dendritic nucleation by two mechanisms, (1) direct activation of Arp2/3 complex and (2) stabilization of newly generated filament branch points. By these mechanisms, cortactin may promote the formation and stabilization of the actin network that drives protrusion at the leading edge of migrating cells.

Cortactin localization to sites of actin assembly in lamellipodia requires interactions with F-actin and the Arp2/3 complex

Cortactin is an actin-binding protein that is enriched within the lamellipodia of motile cells and in neuronal growth cones. Here, we report that cortactin is localized with the actin-related protein (Arp) 2/3 complex at sites of actin polymerization within the lamellipodia. Two distinct sequence motifs of cortactin contribute to its interaction with the cortical actin network: the fourth of six tandem repeats and the amino-terminal acidic region (NTA). Cortactin variants lacking either the fourth tandem repeat or the NTA failed to localize at the cell periphery. Tandem repeat four was necessary for cortactin to stably bind F-actin in vitro. The NTA region interacts directly with the Arp2/3 complex based on affinity chromatography, immunoprecipitation assays, and binding assays using purified components. Cortactin variants containing the NTA region were inefficient at promoting Arp2/3 actin nucleation activity. These data provide strong evidence that cortactin is specifically localized to sites of dynamic cortical actin assembly via simultaneous interaction with F-actin and the Arp2/3 complex. Cortactin interacts via its Src homology 3 (SH3) domain with ZO-1 and the SHANK family of postsynaptic density 95/dlg/ZO-1 homology (PDZ) domain-containing proteins, suggesting that cortactin contributes to the spatial organization of sites of actin polymerization coupled to selected cell surface transmembrane receptor complexes.

Stable antisense RNA expression neutralizes the activity of low-density lipoprotein receptor-related protein and promotes urokinase accumulation in the medium of an astrocytic tumor cell line

Low-density lipoprotein receptor-related protein (LRP) binds and internalizes multiple ligands that are structurally and functionally diverse. However, the effects of LRP on cellular phenotype remain unclear. To study LRP in human astrocytic tumor cells, we designed LRP antisense RNA expression constructs in which the antisense cDNA fragment was expressed under the control of the cytomegalovirus (CMV) promoter. U-1242 MG astrocytic tumor cells were transfected with the antisense constructs and cloned from single cells to yield multiple cell lines with decreased LRP expression. Further studies were performed with two cell lines in which LRP antigen was completely eliminated (L(alpha)42) or substantially decreased (Lalpha47), as determined by Western blot analysis. Untransfected U-1242 MG cells and cells that were stably transfected with empty vector (pBK-CMV) bound activated alpha2-macroglobulin (alpha2M) in a specific and saturable manner. The Bmax was about 5000 receptors/cell. Lalpha42 cells did not bind alpha2M, and binding was decreased by >60% in Lalpha47 cells. Lalpha42 and Lalpha47 cells also demonstrated reduced susceptibility to the cytotoxin, Pseudomonas exotoxin A, and accumulated greatly increased levels of urokinase-type plasminogen activator (uPA) in conditioned medium. The accumulation of uPA demonstrates a major role for LRP in the catabolism of this protein in astrocytic tumor cells. The LRP-deficient cell lines, developed using antisense technology, represent a new model system for studying LRP function in astrocytes.

Activated alpha 2-macroglobulin reverses the immunosuppressive activity in human breast cancer cell-conditioned medium by selectively neutralizing transforming growth factor-beta in the presence of interleukin-2

The immunosuppressive activity of tumor cells may be mediated by tumor-derived cytokines such as transforming growth factor-beta (TGF-beta) and interleukin-10 (IL-10). A human breast cancer cell line derived from malignant ascites (BRC 173) secreted TGF-beta, but not IL-10, into tissue culture supernatant (TCS). BRC 173 TCS suppressed natural killer (NK) and lymphokine-activated killer (LAK) cell activity and also blocked the generation of HLA-A*0201-restricted tumor-reactive cytotoxic T-lymphocyte (CTL) lines in vitro. Human alpha 2-macroglobulin (alpha 2M), a plasma protein and cytokine carrier that binds isoforms in the TGF-beta family, was tested for its ability to neutralize the immunosuppressive activity in BRC 173 TCS. alpha 2M was converted to its activated conformation by reaction with methylamine (alpha 2M-MA) and then incubated with normal human peripheral blood lymphocytes (PBL) in the presence of IL-2 and BRC 173 TCS. Lysis of NK targets (K562) and LAK cell targets (DM6 melanoma) by the PBL was examined after 6 days of culture. PBL cultured in IL-2, without TCS or alpha 2M-MA, were lytic for both target cells. BRC 173 TCS substantially suppressed the lytic activity of the PBL in the presence of IL-2. When TGF-beta-neutralizing antibody was added to the PBL culture medium with IL-2 and TCS, a majority of the lytic activity was restored. alpha 2M-MA (280 nM) neutralized almost all of the immunosuppressive activity in the TCS, restoring 80-100% of the lytic activity without any apparent effect on the activity of IL-2. The ability of alpha 2M-MA to counteract immunosuppressive cytokines in breast cancer TCS was evident in serum-containing and serum-free medium. These studies demonstrate the activated alpha 2M can function as a selective cytokine neutralizer to thereby promote the activation of NK, LAK, and tumor-specific CTL responses.

LDL receptor family-dependent and -independent pathways for the internalization and digestion of lipoprotein lipase-associated beta-VLDL by rat vascular smooth muscle cells

Lipoprotein lipase (LPL) promotes the binding and internalization of beta-VLDL (very low density lipoprotein) by many cell types. We examined the function of receptors in the LDL receptor family (LRF) and heparan sulfate proteoglycans (HSPG) in the metabolism of LPL-associated beta-VLDLa by rat vascular smooth muscle cells (VSMCs) in culture. These cells express LDL receptor-related protein and the VLDL receptor, but not the LDL receptor. LPL greatly increased the binding of 125I-labeled beta-VLDL to VSMCs at 4 degrees C. Binding was almost entirely inhibited by heparin, but essentially unaffected by the potent LRF-antagonist, receptor-associated protein (RAP), indicating that LRFs do not contribute significantly to the VSMC binding capacity for LPL-associated beta-VLDL. At 37 degrees C, RAP inhibited the rapid internalization of LPL-associated 125I-labeled beta-VLDL and the digestion of the beta-VLDL into trichloroacetic acid soluble radioactivity; these processes still occurred, but at a decreased rate. RAP did not inhibit the ability of beta-VLDL-LPL complex to stimulate VSMC ACAT activity. Furthermore, in Oil red-O histochemistry experiments, which model foam cell transformation in vitro, RAP paradoxically increased cholesteryl ester storage in VSMCs treated with beta-VLDL and LPL under specific cell culture conditions. These results support a model in which the internalization of LPL-associated beta-VLDL by VSMCs is mediated by two pathways, one involving LRFs and a second that is independent of LRFs, probably involving direct uptake by HSPG. The LRF-dependent pathway leads to less cellular storage of cholesteryl ester and thus may be antiatherogenic under certain conditions.

Embryonic fibroblasts that are genetically deficient in low density lipoprotein receptor-related protein demonstrate increased activity of the urokinase receptor system and accelerated migration on vitronectin

Low density lipoprotein receptor-related protein (LRP) mediates the endocytosis of diverse ligands, including urokinase plasminogen activator (uPA) and its receptor, uPAR, which have been implicated in cellular migration. The purpose of this study was to determine whether LRP affects cellular migration. Murine embryonic fibroblasts (MEF) that are LRP-deficient due to targeted gene disruption and exotoxin selection (MEF-2), heterozygous fibroblasts (PEA-10), and wild-type fibroblasts (MEF-1) were compared. When cultures were denuded of cells in a 1-mm-wide strip, all three cell types migrated into the denuded area. The MEF-2 cells migrated nearly twice as rapidly as the MEF-1 cells or PEA-10 cells. The difference in migration velocity was duplicated in culture wells that were precoated with serum or vitronectin and partially duplicated in wells coated with fibronectin but not in wells coated with type I collagen or Matrigel. uPA was detected in MEF-2 conditioned medium (CM) at a concentration of 0.30 +/- 0.02 nM, which was 13-fold higher than the level detected in MEF-1 CM or PEA-10 CM, suggesting one potential mechanism for the enhanced migration of MEF-2 cells. uPAR was also increased on MEF-2 cells by 4-5-fold, as determined by PI-PLC release, and by 2.5-fold, as determined by a uPA/uPAR activity assay. Mannosamine treatment, which down-regulates cell-surface uPAR, decreased MEF-2 migration by 40% without significantly affecting MEF-1 migration. MEF-2 CM, which is uPA-rich, increased the rate of MEF-1 migration, and MEF-1 CM did not. These studies demonstrate alterations in cellular migration and in the activity of the uPA/uPAR system which accompany complete deficiency of LRP expression in fibroblasts. We propose that uPA and uPAR form an autocrine loop for promoting fibroblast migration and that LRP counteracts the activity of this system.

Proteinases are isoform-specific regulators of the binding of transforming growth factor beta to alpha 2-macroglobulin

alpha 2-Macroglobulin (alpha 2M) regulates growth and gene expression in many cell types by binding and neutralizing transforming growth factor beta (TGF-beta). In this study we characterized the effects of the serine proteinase, plasmin, on the interaction of alpha 2M with TGF-beta 1 and TGF-beta 2. Binding of both TGF-beta isoforms to purified alpha 2M-plasmin complex was primarily non-covalent and reversible. The binding affinity of alpha 2M for TGF-beta 1 was increased by plasmin; the Kd values were 320 and 84 nM for native alpha 2M and alpha 2M-plasmin respectively. In contrast the affinity of alpha 2M for TGF-beta 2 was decreased by plasmin; the Kd values were 14 and 80 nM for native alpha 2M and alpha 2M-plasmin respectively. Thrombin decreased the affinity of alpha 2M for TGF-beta 2 in a similar manner to plasmin. In assays of DNA synthesis in fetal bovine heart endothelial cells, native alpha 2M neutralized the activity of exogenously added TGF-beta 2, whereas alpha 2M-plasmin, at equivalent concentrations, had almost no effect. Native alpha 2M and methylamine-modified alpha 2M increased platelet-derived growth factor alpha-receptor expression in vascular smooth-muscle cells, an activity attributed to the neutralization of autocrine TGF-beta activity, whereas alpha 2M-plasmin was less effective at the same concentration. These studies demonstrate that the effects of proteinases on the cytokine-binding and cytokine-neutralizing activities of alpha 2M are cytokine-dependent. By reacting with alpha 2M, proteinases might regulate not only the availability of cytokines in the extracellular spaces but also the composition of the cytokine milieu.

Epidermal growth factor and platelet-derived growth factor-BB induce a stable increase in the activity of low density lipoprotein receptor-related protein in vascular smooth muscle cells by altering receptor distribution and recycling

Low density lipoprotein receptor-related protein (LRP) is a multifunctional receptor, expressed by vascular smooth muscle cells (VSMCs) in normal arteries and in atherosclerotic lesions. In this investigation, we demonstrate a novel mechanism for the regulation of LRP activity in cultured rat aortic VSMCs. Cells that were treated with platelet-derived growth factor-BB (PDGF-BB) or epidermal growth factor (EGF) for 24 h bound increased amounts of the LRP ligand, activated alpha2-macroglobulin (alpha2M), at 4 degrees C. The Bmax for activated alpha2M was increased from 56 +/- 5 to 178 +/- 24 and 143 +/- 11 fmol/mg cell protein by PDGF-BB and EGF, respectively, while the KD was unchanged. Northern and Western blot analyses demonstrated that neither PDGF-BB nor EGF increase LRP mRNA or protein levels. Instead, LRP was redistributed to the cell surface and remained localized primarily in coated pits, as determined by surface protein biotinylation, affinity labeling, and immunoelectron microscopy studies. The increase in cell-surface LRP was partially explained by a 50% decrease in receptor endocytosis rate; however, at 37 degrees C, PDGF-BB- and EGF-treated VSMCs still bound/internalized increased amounts of activated alpha2M and subsequently released increased amounts of trichloroacetic acid-soluble radioactivity. The cytokine-induced shifts in LRP subcellular distribution were stable when VSMCs were challenged with a saturating concentration of ligand and then incubated, in the absence of cytokine, for 2.5 h at 37 degrees C. Regulation of LRP distribution and activity may be an important aspect of the VSMC response to the atherogenic cytokines, PDGF-BB and EGF.

Native and activated forms of alpha 2-macroglobulin increase expression of platelet-derived growth factor alpha-receptor in vascular smooth muscle cells. Evidence for autocrine transforming growth factor-beta activity

Cellular response to platelet-derived growth factor AA (PDGF-AA) is mediated exclusively by the PDGF alpha-receptor. Vascular smooth muscle cells (VSMCs) in culture typically express very low levels of alpha-receptor. In this study, we demonstrate that the proteinase inhibitor and cytokine carrier alpha 2-macroglobulin (alpha 2M) increases rat VSMC PDGF alpha-receptor expression. PDGF alpha-receptor mRNA levels increased 3-fold by 6 h and were sustained at that level through 24 h in VSMCs treated with 280 nM methylamine-modified alpha 2M (alpha 2M-MA), a form of activated alpha 2M. PDGF beta-receptor mRNA levels were unchanged in the same time period. In 125I-PDGF-AA binding experiments, treatment of VSMCs with alpha 2M-MA increased the maximum binding capacity (Bmax) from 1.9 to 9.2 fmol/mg of cell protein without affecting binding affinity (KD approximately 80 pM). alpha 2M-MA also increased the VSMC response to PDGF-AA as determined by tyrosine phosphorylation of a 170-kDa band, corresponding in mass to the PDGF alpha-receptor. The native form of alpha 2M was comparable to alpha 2M-MA in its ability to increase PDGF-AA binding to VSMCs and tyrosine phosphorylation of the 170-kDa band. Recombinant and proteolytic alpha 2M derivatives were used to demonstrate that alpha 2M increases PDGF alpha-receptor expression by binding VSMC-secreted cytokine(s) and interrupting an autocrine loop that ordinarily suppresses alpha-receptor expression in these cells. Transforming growth factor-beta-neutralizing antibody mimicked the activity of alpha 2M, increasing the binding capacity of VSMCs for PDGF-AA. This study demonstrates that VSMC PDGF alpha-receptor expression and responsiveness to PDGF-AA are regulated by autocrine transforming growth factor-beta activity, potentially other autocrine growth factors, and alpha 2M.

Activated alpha 2-macroglobulin promotes mitogenesis in rat vascular smooth muscle cells by a mechanism that is independent of growth-factor-carrier activity

Vascular smooth muscle cell (vSMC) proliferation is important in atherosclerosis. We previously demonstrated that methylamine-activated alpha 2-macroglobulin (alpha 2M) and transforming growth factor beta 1 (TGF-beta 1) cause a synergistic proliferative response in quiescent rat aortic vSMCs [Stouffer, G. A., La-Marre, J., Gonias, S. L. & Owens, G. K. (1993) J. Biol. Chem. 268, 18,340-18,344]. The first goal of this study was to determine whether the synergy is due to the ability of alpha 2M-methylamine (alpha 2M-MeNH2) to bind TGF-beta 1 and target the growth factor to vSMCs that express the alpha 2M receptor. Receptor-recognized alpha 2M derivatives without TGF-beta 1-binding activity, including ternary alpha 2M-trypsin, an 18-kDa proteolytic fragment of the alpha 2M subunit, and the corresponding recombinant receptor-binding fragment (rRBF) increased vSMC [3H]thymidine incorporation and cell number in a manner similar to alpha 2M-MeNH2. In combination with TGF-beta 1, each alpha 2M derivative caused a synergistic vSMC proliferative response. vSMCs responded comparably when treated with alpha 2M-MeNH2 and TGF-beta 1 simultaneously or in sequence. Furthermore, alpha 2M-MeNH2-TGF-beta 1 complexes increased [3H]thymidine incorporation no more than alpha 2M-MeNH2 alone. These results indicate that TGF-beta 1 binding to alpha 2M is not responsible for the synergistic mitogenic activity. Additional studies were undertaken to determine whether activated alpha 2M independently induces a signal-transduction response in vSMCs. alpha 2M-MeNH2 and rRBF caused a rapid, transient increase in vSMC inositol 1,4,5-trisphosphate. This response was pertussis-toxin insensitive. Receptor-associated protein (RAP; 170 nmol/L) inhibited 91-95% of the specific binding of 125I-alpha 2M-MeNH2 and 125I-rRBF to vSMC; however, RAP did not affect the inositol 1,4,5-trisphosphate response or the mitogenic response. These studies suggest that vSMCs express a receptor, other than low-density-lipoprotein-receptor-related protein, that transduces a signal in response to activated alpha 2M. This receptor may mediate the mitogenic activity of alpha 2M in vSMC culture.

Use of monoclonal anti-light subunit antibodies to study the structure and function of the Entamoeba histolytica Gal/GalNAc adherence lectin

Adherence of Entamoeba histolytica trophozoites to host cells is mediated by a galactose (Gal) and N-acetylgalactosamine (GalNAc)-specific surface lectin. The lectin is a heterodimeric protein composed of heavy (170 kDa) and light (35-31 kDa) subunits linked by disulfide bonds. Polyclonal and monoclonal antibodies (mAb) raised against a light subunit-glutathione-S-transferase fusion protein were used to probe its structure and function. Four light subunit-specific mAb were produced which recognized distinct epitopes on five different light subunit isoforms. Immunoblots with these mAb demonstrated co-migration of light and heavy subunits when nonreduced trophozoite proteins were analysed by SDS-PAGE, indicating that the subunits do not exist free of the heterodimer in significant quantities. While anti-heavy subunit antibodies had previously been shown to alter adherence, anti-light subunit antibodies did not, suggesting that the heavy subunit contains the carbohydrate recognition domain.

Hyperinsulinemia after pancreatic transplantation. Prediction by a novel computer model and in vivo verification

OBJECTIVE

The authors evaluated systemic venous insulin release as a cause of the hyperinsulinemia (HNS) associated with pancreatic transplantation (PTX) with respect to the mechanism and metabolic consequences.

SUMMARY BACKGROUND DATA

Many investigators believe the postoperative anatomy associated with common PTX techniques to be the sole cause of the two- to threefold posttransplantation HINS. However, this concept remains to be conclusively proved and characterized quantitatively.

METHODS

The authors used three approaches to achieve their objectives. First, a computer model was generated based on established data concerning blood flow and tissue insulin extraction to determine whether it was mathematically possible for HINS to be caused by systemic insulin release. Second, HINS clamps were applied to normal dogs using the Andres clamp technique to quantify the in vivo differences in peripheral insulin levels and the metabolic consequences of systemic versus portal insulin infusion. Third, prolonged insulin half-life was evaluated as a possible mechanism of HINS from systemic insulin release by determination of biexponential rates of plasma disappearance from an endogenous pulse of insulin in surgically induced dog models of systemic and portal insulin release.

RESULTS

First, the computer model calculated a 1.4- to 2.9-fold increase in peripheral venous insulin levels with systemic versus portal insulin release, verifying mathematically the concept of HINS resulting from systemic insulin release. Second, the actual systemic insulin infusion produced a 1.3- to 1.4-fold increase in peripheral venous insulin levels compared with portal infusion (p < 0.05). No significant differences in hepatic glucose output, total glucose disposal, or glucose infusion requirements were seen. Third, although the basal insulin level was twofold higher in the surgically induced animal models with systemic insulin release (p < 0.003), there were no differences in biexponential insulin clearance parameters.

CONCLUSIONS

The HINS produced by systemic insulin release did not significantly alter glucose metabolism and was not the result of altered peripheral insulin clearance parameters. In vivo systemic venous insulin infusion studies produce HINS, but not to the degree calculated by mathematic modeling or that occurs after clinical PTX, making it likely that other factors also play a role in the HINS after PTX.

Immersion scald burns: strategies for prevention

Tap water scald burns are common injuries to persons with disabilities, young children, and the elderly. A case is reported of an elderly woman with a physical and neurological handicap who while bathing received partial and full thickness (tap water) scald burns covering 20% of her total body surface area. This life-threatening injury could have been prevented with a Shower Safe, Inc. temperature-controlling water valve.

Beta-1,3-glucanase of sea urchin eggs: release from particles at fertilization

beta-1,3-Glucanase is a latent enzyme found in large and small particles in unfertilized eggs. At fertilization, the enzyme in the large particles is released into the surrounding perivitelline space. The enzyme may be involved in transformations of extracellular glycoproteins.