Linkage, Empowerment, and Access to Prevent Hypertension: A Novel Program to Prevent Hypertension and Reduce Cardiovascular Health Disparities in Detroit, Michigan

BACKGROUND

Serious cardiovascular health disparities persist across the United States, disproportionately affecting Black communities. Mounting evidence supports negative social determinants of health (SDoH) as contributing factors to a higher prevalence of hypertension along with lower control rates. Here, we describe a first-of-a-kind approach to reducing health disparities by focusing on preventing hypertension in Black adults with elevated blood pressure (BP) living in socially vulnerable communities.

METHODS AND RESULTS

Linkage, Empowerment, and Access to Prevent Hypertension (LEAP-HTN) is part of the RESTORE (Addressing Social Determinants to Prevent Hypertension) health equity research network. The trial will test if a novel intervention reduces systolic BP (primary outcome) and prevents the onset of hypertension over 1 year versus usual care in 500 Black adults with elevated BP (systolic BP 120-129 mm Hg; diastolic BP <80 mm Hg) in Detroit, Michigan. LEAP-HTN leverages our groundbreaking platform using geospatial health and social vulnerability data to direct the deployment of mobile health units (MHUs) to communities of greatest need. All patients are referred to primary care providers. Trial participants in the active limb will receive additional collaborative care delivered remotely by community health workers using an innovative strategy termed pragmatic, personalized, adaptable approaches to lifestyle, and life circumstances (PAL2) which mitigates the impact of negative SDoH.

CONCLUSIONS

LEAP-HTN aims to prevent hypertension by improving access and linkage to care while mitigating negative SDoH. This novel approach could represent a sustainable and scalable strategy to overcoming health disparities in socially vulnerable communities across the United States.

Abstract P380: Linkage, Empowerment, and Access to Prevent Hypertension: A Novel Program to Prevent Hypertension and Reduce Cardiovascular Health Disparities in Detroit Michigan

Background: Serious health disparities persist across the United States (US) whereby Black communities suffer a disproportionate burden of cardiovascular diseases. A higher prevalence of hypertension along with lower control rates are major contributing factors; while mounting evidence supports that negative social determinants of health (SDoH) play a causal role. Here, we describe a first-of-a-kind approach to reduce health disparities by focusing on preventing hypertension in Black adults with elevated blood pressure (BP) living in socially vulnerable communities.

Methods and Results: LEAP-HTN (Linkage, Empowerment, and Access to Prevent Hypertension) is part of the RESTORE (Addressing Social Determinants to Prevent Hypertension) Health Equity Research Network, a $20 Million initiative funded by the American Heart Association. The trial will test if a novel intervention reduces systolic blood pressure (BP) (primary outcome) and prevents the onset of hypertension over one year versus usual care in 500 Black adults with elevated BP (systolic BP 120-129 mm Hg; diastolic BP <80 mm Hg) in Detroit, Michigan. LEAP-HTN improves access to health care by leveraging our groundbreaking platform using geospatial health and social vulnerability data to direct deployment of mobile health units (MHUs) to communities of greatest need. Preliminary data suggest that 10% of patients screened for HTN in the MHUs would meet BP inclusion criteria. All patients are referred to primary care providers. Trial participants in the active limb will receive additional collaborative care delivered remotely by community health workers using an innovative strategy termed PAL 2 (Pragmatic, Personalized, Adaptable Approaches to Lifestyle and Life Circumstance)(Figure). PAL 2 emphasizes the mitigation of negative SDoH, thereby reducing allostatic load while fostering greater success in achieving lifestyle changes.

Conclusions: LEAP-HTN aims to lower BP and prevent hypertension by improving access and linkage to healthcare while mitigating negative SDoH. Through an innovative patient-centered intervention, PAL 2 , our program model may represent a sustainable and scalable strategy to help overcome persistent health disparities in socially vulnerable communities across the US.

Does Vitamin D Provide Added Benefit to Antihypertensive Therapy in Reducing Left Ventricular Hypertrophy Determined by Cardiac Magnetic Resonance?

BACKGROUND

Left ventricular hypertrophy (LVH) and vitamin D deficiency have been linked to hypertension (HTN) and cardiovascular disease, particularly in African Americans (AAs). Our objective was to determine if the addition of vitamin D to antihypertensive therapy would lead to greater regression of LV mass index (LVMI) as determined by cardiac magnetic resonance (CMR) after 1 year in vitamin D deficient AA patients with uncontrolled HTN and LVH.

METHODS

This study was a randomized, double-blind, placebo-controlled, single-center study. AA patients with HTN (systolic blood pressure [BP] >160 mm Hg), increased LVMI, and vitamin D deficiency (<20 ng/ml) were randomized. All patients received antihypertensive therapy combined with biweekly 50,000 IU vitamin D3 (vitamin D group, n = 55) or placebo (placebo group, n = 58).

RESULTS

At 1 year, there were no statistical differences between the vitamin D and placebo groups in LVMI (-14.1 ± 14.6 vs. -16.9 ± 13.1 g/m2; P = 0.34) or systolic BP (-25.6 ± 32.1 vs. -25.7 ± 25.6 mm Hg; P = 0.99) reduction, respectively. Serum vitamin D levels increased significantly in the vitamin D group compared with placebo (12.7 ± 2.0 vs. 1.8 ± 8.2 ng/ml; P < 0.001).

CONCLUSIONS

In this high-risk cohort of AAs we did not find an association between vitamin D supplementation and differential regression of LVMI or reduction in systolic BP. However, our study suffered from a small sample size with low statistical power precluding a definitive conclusion on the therapeutic benefit of vitamin D in such patients.

CLINICAL TRIALS REGISTRATION

Trial Number NCT01360476. Full trial protocol is available from corresponding author.

Nitroglycerin Use in the Emergency Department: Current Perspectives

Nitroglycerin, a fast-acting vasodilator, is commonly used as a first-line agent for angina in the emergency department and to manage chest pain due to acute coronary syndromes. It is also a treatment option for other disease states such as acute heart failure, pulmonary edema, and aortic dissection. Nitroglycerin is converted to nitric oxide, a potent vasodilator, in the body, leading to venodilation at lower dosages and arteriodilation at higher dosages that results in both preload and afterload reduction, respectively. Although nitroglycerin has historically been administered as a sublingual tablet and/or spray, it is often given intravenously in the emergency department as this enables titration to effect with predictable pharmacokinetics. In this review article, we outline the indications, mechanism of action, contraindications, and adverse effects of nitroglycerin as well as review relevant literature and make general recommendations regarding the use of nitroglycerin in the emergency department.

Public Housing Resident Perspectives on Smoking, Barriers for Smoking Cessation, and Changes in Smoking Mandates

Background

Individuals from low-income groups report disproportionate rates of cigarette use, secondhand smoke (SHS) exposure with increased morbidity and mortality. Smoking bans in public housing have been enacted in attempt to reduce tobacco use and SHS exposure among lower income individuals. This study investigated the support needs of tobacco users living in two public housing complexes in Detroit, Michigan (USA), including their perspectives on smoking, resources and barriers for smoking cessation, and the impact of policy changes.

Methods

This is a mixed-methods study, using a qualitative focus groups approach and a short survey, public housing residents interview data was analyzed to explore themes related to smoking-related issues. Specifically, six themes were assessed across four focus groups: (1) Quitting Smoking, (2) Current Smoking Cessation Resources, (3) Legal Mandates, (4) Education and Perceptions of Smoking, (5) Community Needs and Barriers, and (6) Medical Experiences.

Results

There were 59 participants; the majority (39/42, 93%) of smokers reported at least one quit attempt. During the focus groups, several participants indicated a desire to quit smoking but reported barriers to smoking cessation, such as lack of access to medications, social triggers to continue smoking, and socioeconomic stressors. A number of suggestions were provided to improve smoking cessation resources, including support groups, graphic images of smoking-related diseased tissue, and better communication with health care providers.

Conclusions

These findings demonstrate smoking bans in two public housing complexes can be effective yet are dependent upon a complex set of issues, including numerous barriers to care.

Randomized Controlled Trial of a Novel Silicone Device for the Packing of Cutaneous Abscesses in the Emergency Department: A Pilot Study

Objective

Traditional treatment of abscesses in the emergency department includes packing with gauze; however, this can add pain and discomfort to the procedure and frequently involves a follow-up visit for packing removal. Alternatives to gauze packing have been proposed, but they may have disadvantages in the context of emergency care. The objective of this pilot study was to investigate the use of a novel silicone packing device — the Derma-Stent.

Methods

This was a randomized controlled pilot study of 50 patients from two urban emergency departments with uncomplicated superficial abscesses. The primary outcome was the likelihood of self-removal of packing gauze versus the silicone device. Secondary outcome measures included subjective clinician and patient metrics, such as pain and ease of use.

Results

Patients identified with simple cutaneous abscesses were randomized to intervention (packing with the novel silicone device, n=25) or standard care (gauze packing, n=25). Mean age was 36 years, 54% were female, and 96% identified as African American. Although it took longer to place, the silicone device (19.0 vs 15.3 minutes, p=0.03), pain scores were significantly lower (4.3/10 vs 7.1/10, p=0.008) and ease of use reported by physicians better in the silicone-device group (4.8/5 vs 4.0/5, p=0.002). A high unknown rate in the gauze-packing group limits discussion of the likelihood of self-removal; however, the silicone device was more likely to remain in place (60%) versus the gauze packing at 3 days (24%, p=0.01).

Conclusion

This pilot randomized controlled trial compared the treatment of packing cutaneous abscesses with gauze versus using the silicone device. Limitations in the data prevent discussion on likelihood of self-removal. However, the silicone device was more likely to remain in place at day 3 follow-up and was equally effective to gauze packing in abscess reduction while also improving patient-reported pain scores. It did take longer to place the silicone device; however, physicians reported better ease of use and removal. This pilot study is encouraging for additional larger-scale trials that are required to further assess the utility of this device in the emergency department.

Ultra-high dose intravenous nitroglycerin in an ESRD patient with acutely decompensated heart failure

Acute cardiogenic pulmonary edema is a highly unstable and potentially lethal condition that is most commonly associated with markedly elevated blood pressure (BP). Use of nitrates, diuretics, and non-invasive positive pressure ventilatory support are the mainstays of early intervention and stabilization. Use of high-dose bolus intravenous nitroglycerin, which causes both preload and afterload reduction, has shown significant promise in studies to date, reducing the need for endotracheal intubation (ETI) and intensive care unit admission. To date, the highest recorded total dose of nitroglycerin used during the initial stabilization of acute pulmonary edema has been 20 mg. Here, we describe a patient with end-stage renal disease who developed acute cardiogenic pulmonary edema and received a total of 59 mg nitroglycerin (56 mg push dose intravenous + 3 mg intravenous drip) over 41 minutes leading to successful stabilization and avoidance of ETI, facilitating rapid initiation of emergent hemodialysis.

Angiotensin-converting enzyme inhibitors increase anti-fibrotic biomarkers in African Americans with left ventricular hypertrophy

Angiotensin‐converting enzyme inhibitors (ACEi) are part of the indicated treatment in hypertensive African Americans. ACEi have blood pressure‐independent effects that may make them preferred for certain patients. We aimed to evaluate the impact of ACEi on anti‐fibrotic biomarkers in African American hypertensive patients with left ventricular hypertrophy (LVH). We conducted a post hoc analysis of a randomized controlled trial in which hypertensive African American patients with LVH and vitamin D deficiency were randomized to receive intensive antihypertensive therapy plus vitamin D supplementation or placebo. We selected patients who had detectable lisinopril (lisinopril group) in plasma using liquid‐chromatography/mass spectrometry analysis and compared them to subjects who did not (comparison group) at the one‐year follow‐up. The pro‐fibrotic marker type 1 procollagen C‐terminal propeptide (PICP) and the anti‐fibrotic markers matrix metalloproteinase‐1 (MMP‐1), tissue inhibitor of metalloproteinases 1 (TIMP‐1), telopeptide of collagen type I (CITP), and N‐acetyl‐seryl‐aspartyl‐lysyl‐proline (Ac‐SDKP) peptide were measured. Sixty‐six patients were included, and the mean age was 46.2 ± 8 years. No difference was observed in the number and intensity of antihypertensive medications prescribed in each group. Patients with detectable lisinopril had lower blood pressure than those in the comparison group. The anti‐fibrotic markers Ac‐SDKP, MMP‐1, and MMP‐1/TIMP‐1 ratio were higher in patients with detectable ACEi (all p < .05). In a model adjusted for systolic blood pressure, MMP‐1/TIMP‐1 (p = .02) and Ac‐SDKP (p < .001) levels were associated with lisinopril. We conclude that ACEi increase anti‐fibrotic biomarkers in hypertensive African Americans with LVH, suggesting that they may offer added benefit over other agents in such patients.

Effect of Lower Blood Pressure Goals on Left Ventricular Structure and Function in Patients With Subclinical Hypertensive Heart Disease

BACKGROUND

Subclinical hypertensive heart disease (SHHD) is a precursor to heart failure. Blood pressure (BP) reduction is an important component of secondary disease prevention in patients with SHHD. Treating patients with SHHD utilizing a more intensive BP target (120/80 mm Hg), may lead to improved cardiac function but there has been limited study of this, particularly in African Americans (AAs).

METHODS

We conducted a single center, randomized controlled trial where subjects with uncontrolled, asymptomatic hypertension, and SHHD not managed by a primary care physician were randomized to standard (<140/90 mm Hg) or intensive (<120/80 mm Hg) BP therapy groups with quarterly follow-up for 12 months. The primary outcome was the differences of BP reduction between these 2 groups and the secondary outcome was the improvement in echocardiographic measures at 12 months.

RESULTS

Patients (95% AAs, 65% male, mean age 49.4) were randomized to the standard (n = 65) or the intensive (n = 58) BP therapy groups. Despite significant reductions in systolic BP (sBP) from baseline (-10.9 vs. -19.1 mm Hg, respectively) (P < 0.05), no significant differences were noted between intention-to-treat groups (P = 0.33) or the proportion with resolution of SHHD (P = 0.31). However, on post hoc analysis, achievement of a sBP <130 mm Hg was associated with significant reduction in indexed left ventricular mass (-6.91 gm/m2.7; P = 0.008) which remained significant on mixed effect modeling (P = 0.031).

CONCLUSIONS

In post hoc analysis, sBP <130 mm Hg in predominantly AA patients with SHHD was associated with improved cardiac function and reverse remodeling and may help to explain preventative effects of lower BP goals.

CLINICAL TRIALS REGISTRATION

Trial Number NCT00689819.

Identification of 21,22-Dehydroazaspiracids in Mussels ( Mytilus edulis) and in Vitro Toxicity of Azaspiracid-26

Azaspiracids (AZAs) are marine biotoxins produced by the genera Azadinium and Amphidoma, pelagic marine dinoflagellates that may accumulate in shellfish resulting in human illness following consumption. The complexity of these toxins has been well documented, with more than 40 structural variants reported that are produced by dinoflagellates, result from metabolism in shellfish, or are extraction artifacts. Approximately 34 μg of a new AZA with MW 823 Da (AZA26 (3)) was isolated from blue mussels ( Mytilus edulis), and its structure determined by MS and NMR spectroscopy. AZA26, possibly a bioconversion product of AZA5, lacked the C-20-C-21 diol present in all AZAs reported thus far and had a 21,22-olefin and a keto group at C-23. Toxicological assessment of 3 using an in vitro model system based on Jurkat T lymphocyte cells showed the potency to be ∼30-fold lower than that of AZA1. The corresponding 21,22-dehydro-23-oxo-analogue of AZA10 (AZA28) and 21,22-dehydro analogues of AZA3, -4, -5, -6, -9, and -10 (AZA25, -48 (4), -60, -27, -49, and -61, respectively) were also identified by HRMS/MS, periodate cleavage reactivity, conversion from known analogues, and NMR (for 4 that was present in a partially purified sample of AZA7).

Screening and Treatment for Subclinical Hypertensive Heart Disease in Emergency Department Patients With Uncontrolled Blood Pressure: A Cost-effectiveness Analysis

OBJECTIVES

Poorly controlled hypertension (HTN) is extremely prevalent and, if left unchecked, subclinical hypertensive heart disease (SHHD) may ensue leading to conditions such as heart failure. To address this, we designed a multidisciplinary program to detect and treat SHHD in a high-risk, predominantly African American community. The primary objective of this study was to determine the cost-effectiveness of our program.

METHODS

Study costs associated with identifying and treating patients with SHHD were calculated and a sensitivity analysis was performed comparing the effect of four parameters on cost estimates. These included prevalence of disease, effectiveness of treatment (regression of SHHD, reversal of left ventricular hypertrophy [LVH], or blood pressure [BP] control as separate measures), echocardiogram costs, and participant time/travel costs. The parent study for this analysis was a single-center, randomized controlled trial comparing cardiac effects of standard and intense (<120/80 mm Hg) BP goals at 1 year in patients with uncontrolled HTN and SHHD. A total of 149 patients (94% African American) were enrolled, 133 (89%) had SHHD, 123 (93%) of whom were randomized, with 88 (72%) completing the study. Patients were clinically evaluated and medically managed over the course of 1 year with repeated echocardiograms. Costs of these interventions were analyzed and, following standard practices, a cost per quality-adjusted life-year (QALY) less than $50,000 was defined as cost-effective.

RESULTS

Total costs estimates for the program ranged from $117,044 to $119,319. Cost per QALY was dependent on SHHD prevalence and the measure of effectiveness but not input costs. Cost-effectiveness (cost per QALY less than $50,000) was achieved when SHHD prevalence exceeded 11.1% for regression of SHHD, 4.7% for reversal of LVH, and 2.9% for achievement of BP control.

CONCLUSIONS

In this cohort of predominantly African American patients with uncontrolled HTN, SHHD prevalence was high and screening with treatment was cost-effective across a range of assumptions. These data suggest that multidisciplinary programs such as this can be a cost-effective mechanism to mitigate the cardiovascular consequences of HTN in emergency department patients with uncontrolled BP.

Structure-Activity Relationship Studies Using Natural and Synthetic Okadaic Acid/Dinophysistoxin Toxins

Okadaic acid (OA) and the closely related dinophysistoxins (DTXs) are algal toxins that accumulate in shellfish and are known serine/threonine protein phosphatase (ser/thr PP) inhibitors. Phosphatases are important modulators of enzyme activity and cell signaling pathways. However, the interactions between the OA/DTX toxins and phosphatases are not fully understood. This study sought to identify phosphatase targets and characterize their structure–activity relationships (SAR) with these algal toxins using a combination of phosphatase activity and cytotoxicity assays. Preliminary screening of 21 human and yeast phosphatases indicated that only three ser/thr PPs (PP2a, PP1, PP5) were inhibited by physiologically saturating concentrations of DTX2 (200 nM). SAR studies employed naturally-isolated OA, DTX1, and DTX2, which vary in degree and/or position of methylation, in addition to synthetic 2-epi-DTX2. OA/DTX analogs induced cytotoxicity and inhibited PP activity with a relatively conserved order of potency: OA = DTX1 ≥ DTX2 >> 2-epi-DTX. The PPs were also differentially inhibited with sensitivities of PP2a > PP5 > PP1. These findings demonstrate that small variations in OA/DTX toxin structures, particularly at the head region (i.e., C1/C2), result in significant changes in toxicological potency, whereas changes in methylation at C31 and C35 (tail region) only mildly affect potency. In addition to this being the first study to extensively test OA/DTX analogs’ activities towards PP5, these data will be helpful for accurately determining toxic equivalence factors (TEFs), facilitating molecular modeling efforts, and developing highly selective phosphatase inhibitors.

Structure Elucidation, Relative LC-MS Response and In Vitro Toxicity of Azaspiracids 7-10 Isolated from Mussels (Mytilus edulis)

Azaspiracids (AZAs) are marine biotoxins produced by dinoflagellates that can accumulate in shellfish, which if consumed can lead to poisoning events. AZA7-10, 7-10, were isolated from shellfish and their structures, previously proposed on the basis of only LC-MS/MS data, were confirmed by NMR spectroscopy. Purified AZA4-6, 4-6, and 7-10 were accurately quantitated by qNMR and used to assay cytotoxicity with Jurkat T lymphocyte cells for the first time. LC-MS(MS) molar response studies performed using isocratic and gradient elution in both selected ion monitoring and selected reaction monitoring modes showed that responses for the analogues ranged from 0.3 to 1.2 relative to AZA1, 1. All AZA analogues tested were cytotoxic to Jurkat T lymphocyte cells in a time- and concentration-dependent manner; however, there were distinct differences in their EC50 values, with the potencies for each analogue being: AZA6 > AZA8 > AZA1 > AZA4 ≈ AZA9 > AZA5 ≈ AZA10. This data contributes to the understanding of the structure-activity relationships of AZAs.

Isolation, structure elucidation, relative LC-MS response, and in vitro toxicity of azaspiracids from the dinoflagellate Azadinium spinosum

We identified three new azaspiracids (AZAs) with molecular weights of 715, 815, and 829 (AZA33 (3), AZA34 (4), and AZA35, respectively) in mussels, seawater, and Azadinium spinosum culture. Approximately 700 μg of 3 and 250 μg of 4 were isolated from a bulk culture of A. spinosum, and their structures determined by MS and NMR spectroscopy. These compounds differ significantly at the carboxyl end of the molecule from known AZA analogues and therefore provide valuable information on structure-activity relationships. Initial toxicological assessment was performed using an in vitro model system based on Jurkat T lymphocyte cytotoxicity, and the potencies of 3 and 4 were found to be 0.22- and 5.5-fold that of AZA1 (1), respectively. Thus, major changes in the carboxyl end of 1 resulted in significant changes in toxicity. In mussel extracts, 3 was detected at low levels, whereas 4 and AZA35 were detected only at extremely low levels or not at all. The structures of 3 and 4 are consistent with AZAs being biosynthetically assembled from the amino end.

Epimers of azaspiracids: Isolation, structural elucidation, relative LC-MS response, and in vitro toxicity of 37-epi-azaspiracid-1

Since azaspiracid-1 (AZA1) was identified in 1998, the number of AZA analogues has increased to over 30. The development of an LC-MS method using a neutral mobile phase led to the discovery of isomers of AZA1, AZA2, and AZA3, present at ~2-16% of the parent analogues in phytoplankton and shellfish samples. Under acidic mobile phase conditions, isomers and their parents are not separated. Stability studies showed that these isomers were spontaneous epimerization products whose formation is accelerated with the application of heat. The AZA1 isomer was isolated from contaminated shellfish and identified as 37-epi-AZA1 by nuclear magnetic resonance (NMR) spectroscopy and chemical analyses. Similar analysis indicated that the isomers of AZA2 and AZA3 corresponded to 37-epi-AZA2 and 37-epi-AZA3, respectively. The 37-epimers were found to exist in equilibrium with the parent compounds in solution. 37-epi-AZA1 was quantitated by NMR, and relative molar response studies were performed to determine the potential differences in LC-MS response of AZA1 and 37-epi-AZA1. Toxicological effects were determined using Jurkat T lymphocyte cells as an in vitro cell model. Cytotoxicity experiments employing a metabolically based dye (i.e., MTS) indicated that 37-epi-AZA1 elicited a lethal response that was both concentration- and time-dependent, with EC50 values in the subnanomolar range. On the basis of EC50 comparisons, 37-epi-AZA1 was 5.1-fold more potent than AZA1. This data suggests that the presence of these epimers in seafood products should be considered in the analysis of AZAs for regulatory purposes.

Comparative analysis of three brevetoxin-associated bottlenose dolphin (Tursiops truncatus) mortality events in the Florida Panhandle region (USA)

In the Florida Panhandle region, bottlenose dolphins (Tursiops truncatus) have been highly susceptible to large-scale unusual mortality events (UMEs) that may have been the result of exposure to blooms of the dinoflagellate Karenia brevis and its neurotoxin, brevetoxin (PbTx). Between 1999 and 2006, three bottlenose dolphin UMEs occurred in the Florida Panhandle region. The primary objective of this study was to determine if these mortality events were due to brevetoxicosis. Analysis of over 850 samples from 105 bottlenose dolphins and associated prey items were analyzed for algal toxins and have provided details on tissue distribution, pathways of trophic transfer, and spatial-temporal trends for each mortality event. In 1999/2000, 152 dolphins died following extensive K. brevis blooms and brevetoxin was detected in 52% of animals tested at concentrations up to 500 ng/g. In 2004, 105 bottlenose dolphins died in the absence of an identifiable K. brevis bloom; however, 100% of the tested animals were positive for brevetoxin at concentrations up to 29,126 ng/mL. Dolphin stomach contents frequently consisted of brevetoxin-contaminated menhaden. In addition, another potentially toxigenic algal species, Pseudo-nitzschia, was present and low levels of the neurotoxin domoic acid (DA) were detected in nearly all tested animals (89%). In 2005/2006, 90 bottlenose dolphins died that were initially coincident with high densities of K. brevis. Most (93%) of the tested animals were positive for brevetoxin at concentrations up to 2,724 ng/mL. No DA was detected in these animals despite the presence of an intense DA-producing Pseudo-nitzschia bloom. In contrast to the absence or very low levels of brevetoxins measured in live dolphins, and those stranding in the absence of a K. brevis bloom, these data, taken together with the absence of any other obvious pathology, provide strong evidence that brevetoxin was the causative agent involved in these bottlenose dolphin mortality events.

Marine algal toxin azaspiracid is an open-state blocker of hERG potassium channels

Azaspiracids (AZA) are polyether marine dinoflagellate toxins that accumulate in shellfish and represent an emerging human health risk. Although human exposure is primarily manifested by severe and protracted diarrhea, this toxin class has been shown to be highly cytotoxic, a teratogen to developing fish, and a possible carcinogen in mice. Until now, AZA's molecular target has not yet been determined. Using three independent methods (voltage clamp, channel binding assay, and thallium flux assay), we have for the first time demonstrated that AZA1, AZA2, and AZA3 each bind to and block the hERG (human ether-à-go-go related gene) potassium channel heterologously expressed in HEK-293 mammalian cells. Inhibition of K(+) current for each AZA analogue was concentration-dependent (IC(50) value range: 0.64-0.84 μM). The mechanism of hERG channel inhibition by AZA1 was investigated further in Xenopus oocytes where it was shown to be an open-state-dependent blocker and, using mutant channels, to interact with F656 but not with Y652 within the S6 transmembrane domain that forms the channel's central pore. AZA1, AZA2, and AZA3 were each shown to inhibit [(3)H]dofetilide binding to the hERG channel and thallium ion flux through the channel (IC(50) value range: 2.1-6.6 μM). AZA1 did not block the K(+) current of the closely related EAG1 channel. Collectively, these data suggest that the AZAs physically block the K(+) conductance pathway of hERG1 channels by occluding the cytoplasmic mouth of the open pore. Although the concentrations necessary to block hERG channels are relatively high, AZA-induced blockage may prove to contribute to the toxicological properties of the AZAs.

Global gene expression profiling in larval zebrafish exposed to microcystin-LR and microcystis reveals endocrine disrupting effects of Cyanobacteria

Microcystis blooms occur worldwide and threaten aquatic ecosystems and human health. Sublethal effects on early developmental stages of fish are largely unknown, and research has mainly focused on microcystin toxins (such as MC-LR) rather than Microcystis cells. We exposed (96 h) zebrafish larvae to purified MC-LR (0-1000 μg/L) or lyophilized Microcystis aeruginosa containing 4.5 μg/L MC-LR and evaluated changes in global gene expression (Affymetrix GeneChip zebrafish genome arrays). Significant changes in gene expression (≥ 1.7-fold change, p < 0.0001) were determined with Rosetta Resolver 7.0, and ontology analysis was conducted with the DAVID bioinformatics tool. The number of differentially expressed genes relative to control increased with MC-LR concentration and included genes related to known mechanisms of action for MC-LR in mammals and older life stages of fish, as well as genes unique to larval zebrafish. Up-regulation of vitellogenin genes (vtg) (19.2-fold to >100-fold on arrays; 619.3-fold confirmed by quantitative PCR) was observed in Microcystis-exposed larvae but not in larvae exposed to MC-LR. Up-regulation of vtg indicates exposure to estrogenic substance(s) and suggests that Microcystis may be a natural source of environmental estrogens. Concerns about effects of Microcystis blooms may extend beyond those associated with the microcystin toxin.

Eosinophilia and biotoxin exposure in bottlenose dolphins (Tursiops truncatus) from a coastal area impacted by repeated mortality events

Bottlenose dolphins (Tursiops truncatus) inhabiting coastal waters in the northern Gulf of Mexico have been impacted by recurrent unusual mortality events over the past few decades. Several of these mortality events along the Florida panhandle have been tentatively attributed to poisoning from brevetoxin produced by the dinoflagellate Karenia brevis. While dolphins in other regions of the Florida coast are often exposed to K. brevis blooms, large-scale dolphin mortality events are relatively rare and the frequency and magnitude of die-offs along the Panhandle raise concern for the apparent vulnerability of dolphins in this region. We report results from dolphin health assessments conducted near St. Joseph Bay, Florida, an area impacted by 3 unusual die-offs within a 7-year time span. An eosinophilia syndrome, manifested as an elevated blood eosinophil count without obvious cause, was observed in 23% of sampled dolphins. Elevated eosinophil counts were associated with decreased T-lymphocyte proliferation and increased neutrophil phagocytosis. In addition, indication of chronic low-level exposure to another algal toxin, domoic acid produced by the diatom Pseudo-nitzschia spp., was determined. Previous studies of other marine mammal populations exposed recurrently to Pseudo-nitzschia blooms have suggested a possible link between the eosinophilia and domoic acid exposure. While the chronic eosinophilia syndrome could over the long-term produce organ damage and alter immunological status and thereby increase vulnerability to other challenges, the significance of the high prevalence of the syndrome to the observed mortality events in the St. Joseph Bay area is unclear. Nonetheless, the unusual immunological findings and concurrent evidence of domoic acid exposure in this sentinel marine species suggest a need for further investigation to elucidate potential links between chronic, low-level exposure to algal toxins and immune health.

An extract of Hydrilla verticillata and associated epiphytes induces avian vacuolar myelinopathy in laboratory mallards

Avian vacuolar myelinopathy (AVM) is a neurological disease affecting bald eagles (Haliaeetus leucocephalus), American coots (Fulica americana), waterfowl, and other birds in the southeastern United States. The cause of the disease is unknown, but is thought to be a naturally produced toxin. AVM is associated with aquatic macrophytes, most frequently hydrilla (Hydrilla verticillata), and researchers have linked the disease to an epiphytic cyanobacterial species associated with the macrophytes. The goal of this study was to develop an extraction protocol for separating the putative toxin from a hydrilla-cyanobacterial matrix. Hydrilla samples were collected from an AVM-affected reservoir (J. Strom Thurmond Lake, SC) and confirmed to contain the etiologic agent by mallard (Anas platyrhynchos) bioassay. These samples were then extracted using a solvent series of increasing polarity: hexanes, acetone, and methanol. Control hydrilla samples from a reference reservoir with no history of AVM (Lake Marion, SC) were extracted in parallel. Resulting extracts were administered to mallards by oral gavage. Our findings indicate that the methanol extracts of hydrilla collected from the AVM-affected site induced the disease in laboratory mallards. This study provides the first data documenting for an "extractable" AVM-inducing agent.

Fate and distribution of brevetoxin (PbTx) following lysis of Karenia brevis by algicidal bacteria, including analysis of open A-ring derivatives

Flavobacteriaceae (strain S03) and Cytophaga sp. (strain 41-DBG2) are algicidal bacteria active against the brevetoxin (PbTx)-producing, red tide dinoflagellate, Karenia brevis. Little is known about the fate of PbTx associated with K. brevis cells following attack by such bacteria. The fate and distribution of PbTx in K. brevis cultures exposed to these algicidal strains were thus examined by receptor binding assay and liquid chromatography/mass spectrometry (LC/MS) in three size fractions (>5, 0.22-5, <0.22microm) over a 2-week time course. In control cultures, brevetoxin concentrations in the >5microm particulate size fraction correlated with changes in cell density, whereas significant increases in dissolved (i.e., <0.22microm) toxin were observed in the later stages of culture growth. Exposure of K. brevis to either of the two algicidal bacteria tested caused cell lysis, coinciding with a rapid decline in the >5microm PbTX size fraction and a simultaneous release of dissolved toxin into the growth medium. Upon cell lysis, dissolved brevetoxin accounted for ca. 60% of total toxin and consisted of 51-82% open A-ring derivatives. Open A-ring PbTx-2 and PbTx-3 derivatives bound with lower affinity (approximately 22- and 57-fold, respectively) to voltage-gated sodium channels and were considerably less cytotoxic (86- and 142-fold, respectively) to N2A cells than their individual parent toxins (i.e., PbTx-2 and PbTx-3). These novel findings of changes in PbTx size-fractioned distribution and overall reduction in K. brevis toxicity following attack by algicidal bacteria improve our understanding of potential trophic transfer routes and the fate of PbTx during red tide events. Moreover, this information will be important to consider when evaluating the potential role of algicidal bacteria in harmful algal bloom (HAB) management strategies involving control of bloom populations.

Extraction and analysis of lipophilic brevetoxins from the red tide dinoflagellate Karenia brevis

Efficient extraction and accurate analysis of lipophilic brevetoxins (PbTxs), produced by the harmful algal bloom (HAB) species Karenia brevis, are essential when assessing the toxicological potential of this dinoflagellate. One of the most commonly used brevetoxin extraction methodologies employs C18 solid-phase extraction (SPE). In this study, C18 SPEC discs were tested for extraction of spiked PbTx-3 in seawater and naturally produced brevetoxins from K. brevis. Quantification of brevetoxin in the extracts was determined using four independent methods: receptor binding assay (RBA), radioimmunoassay (RIA), neuroblastoma (N2A) cytotoxicity assay, and liquid chromatography/mass spectrometry (LC/MS). In addition to quantification of the brevetoxin concentration, LC/MS analysis provided identification of individual congeners and each of their hydrolyzed products. SPEC disc extractions prepared from sonicated cultures of non-brevetoxin-producing Karenia mikimotoi cultures spiked with PbTx-3 yielded extraction efficiencies of 108, 99, and 125% as determined by the RBA, RIA, and N2A cytotoxicity assay, respectively. In SPEC disc extracts of brevetoxin-producing K. brevis (isolate SP3) cultures, LC/MS analysis yielded the highest total concentrations, possibly due to the concurrent detection of hydrolytic brevetoxin congeners that accounted for up to 20% of the congener profile. Relative to the brevetoxin concentration as determined by LC/MS, the RBA, RIA, and N2A cytotoxicity assay detected 73, 83, and 51% of the total brevetoxin concentration. Stability experiments demonstrated that brevetoxins remain stable on the SPEC discs for at least 30 days, making this extraction method suitable for shipboard collections.

Azaspiracid-1 inhibits bioelectrical activity of spinal cord neuronal networks

Azaspiracid-1 (AZA-1) is a recently identified phycotoxin that accumulates in molluscs and can cause severe human intoxications. For this study, we utilized murine spinal cord and frontal cortex neuronal networks grown over 64 channel microelectrode arrays (MEAs) to gain insights into the mechanism of action of AZA-1 on neuronal cells. Extracellular recordings of spontaneous action potentials were performed by monitoring mean spike rate as an assay of the efficacy of AZA-1 to alter the bioelectrical activity of neurons in the networks. Via slow onset, AZA-1 decreased the mean spike rate of the spinal cord neurons with an IC(50) of ca. 2.1nM, followed by partial recovery of original activity when toxin was removed. Pre-treatment with the GABA(A) receptor antagonist bicuculline led to an increased response of the neuronal networks to AZA-1 exposure and resulted in an irreversible inhibition of spike rate. AZA-1 did not cause any changes in frontal cortex networks upon drug exposure. In addition, whole-cell patch clamp recordings from spinal cord neurons showed that AZA-1 had no significant effect on the voltage-gated sodium (Na(+)) or calcium (Ca(2+)) currents, suggesting that the toxin affected synaptic transmission in the neuronal networks through a mechanism independent of these voltage-gated channels.

Teratogenic effects of azaspiracid-1 identified by microinjection of Japanese medaka (Oryzias latipes) embryos

Azaspiracid-1 (AZA-1) is a newly identified phycotoxin that accumulates in commercially important bivalve molluscs harvested in several European countries and causes severe human intoxications. Molluscan shellfish are known vectors for accumulation and subsequent transfer of phycotoxins such as brevetoxin and domoic acid through various trophic levels within food webs. Finfish can also accumulate phycotoxins, both directly from toxic algae or from consumption of contaminated shellfish and smaller intoxicated fish. To evaluate the teratogenic potential of AZA-1 and its relevancy to toxin accumulation in finfish, we have utilized a microinjection technique to mimic the maternal-egg toxin transfer of an AZA-1 reference standard and a shellfish extract containing azaspiracids in an embryonic Japanese medaka (Oryzias latipes) fish model. Microinjection of purified AZA-1 caused dose-dependent effects on heart rate, developmental rate, hatching success, and viability in medaka embryos. Within 4 days of exposure to doses > or = 40 pg AZA-1/egg, substantial retardation in development was observed as reduced somatic growth and yolk absorption, and delayed onset of blood circulation and pigmentation. Embryos treated to > or =40 pg AZA-1/egg had slower heart rates (bradycardia) for the 9 days in ovo period, followed by reduced hatching success. Microinjection of a contaminated mussel (Mytilus edulis) extract containing AZAs (AZA-1, -2, and -3), okadaic acid, and dinophysistoxin-2 resulted in similar responses from the fish embryos at equivalent doses. These studies demonstrate that AZA-1 is a potent teratogen to finfish. This work will complement future investigations on AZA-1 accumulation in marine food webs and provide a basis for understanding its toxicity at different trophic levels.

Cytotoxic and cytoskeletal effects of azaspiracid-1 on mammalian cell lines

Azaspiracid-1 (AZA-1) is a newly identified phycotoxin reported to accumulate in molluscs from several northern European countries and documented to have caused severe human intoxications. The mechanism of action of AZA-1 is unknown. Our initial investigations have shown that AZA-1 is cytotoxic to a range of cell types. Cytotoxicity was evident in all seven cell types tested, suggesting a broad-spectrum mode of action, and was both time- and concentration-dependent. However, AZA-1 took an unusually long time (>24 h) to cause complete cytotoxicity in most cell types, with the exception of the rat pituitary GH(4)C(1). Extended exposure times did not always lower the EC(50) value for a given cell line, but always resulted in more complete cytotoxicity over a very narrow concentration range. The Jurkat cell line (human lymphocyte T) appeared to be very sensitive to AZA-1, although the EC(50) values (24-72 h) for all the cell types were in the low nanomolar range (0.9-16.8 nM). The effect of AZA-1 on membrane integrity was tested on Jurkat cells and these data confirm our visual observations of cytotoxicity and necrotic cell lysis following exposure of Jurkat cells to AZA-1 and suggest that AZA-1 has some properties unique among marine algal toxins. Additionally, there were dramatic effects of AZA-1 on the arrangement of F-actin with the concurrent loss of pseudopodia, cytoplasmic extensions that function in mobility and chemotaxis. Although these phycotoxin-specific effects of AZA-1 suggest a possible site of action, further work using cell-based approaches is needed to determine the precise mode of action of AZA-1.

N,N-Dimethylformamide modulates acid extrusion from murine hepatoma cells

N,N-Dimethylformamide (DMF) affects cellular differentiation, causes hepatotoxicity and gastric irritation, and may be carcinogenic. Since these processes involve changes in cellular pH homeostasis, we investigated the effects of DMF on H+ extrusion and cytosolic pH (pHi) of mouse hepatoma cells (Hepa 1C1C7). Extracellular pH was monitored using a silicon-based sensor system (Cytosensor microphysiometer) and pHi was monitored by fluorescence spectrophotometry. Superfusion of cells with DMF (0.25 to 0.5 M) suppressed the extracellular acidification rate (ECAR) below baseline. Following washout of DMF there was a rapid, concentration-dependent, prolonged overshoot of ECAR above baseline rates. Removal of extracellular Na+ or superfusion with amiloride abolished the overshoot in acidification rate, indicating involvement of Na+/H+ exchange. The overshoot was dependent on extracellular glucose, suggesting that it arises from an increase in metabolic acid production. Fluorescence measurements showed that DMF did not change pHi. Furthermore, DMF did not alter the rate of pHi recovery of cells acid loaded using nigericin, indicating that DMF does not directly alter Na+/H+ exchange activity in these cells. In summary, these data suggest that suppression of acidification rate by DMF is likely due to decreased metabolic acid production. Washout of DMF is then accompanied by increased glucose metabolism and H+ efflux via Na+/H+ exchange. It is possible that alterations in H+ production and transport contribute to the hepatotoxicity of DMF and its effects on cellular differentiation.