Tammy Renee Dugas

Objective: To evaluate the effects of metoclopramide and azithromycin on liquid-phase gastric emptying (GE) in a clonidine-induced delayed GE model using the acetaminophen absorption test (AAT). Methods: This was a randomized crossover study of healthy, purpose-bred, mixed-breed dogs performed in a controlled laboratory setting from May through July 2023. Dogs received 1 of 4 treatments 1 hour before ingesting a liquid meal containing 25% of their resting energy requirement and 20 mg/kg acetaminophen: no treatment (control), clonidine (0.03 mg/kg, SC), clonidine plus azithromycin (4 mg/kg, IV), or clonidine plus metoclopramide (0.5 mg/kg, SC). Using high-power liquid chromatography, plasma acetaminophen concentrations were measured in 11 samples collected preprandially and at 10 time points between 0.5 and 24 hours postprandially. Time to peak concentration was used as a proxy for GE time. Results were analyzed by 2-way ANOVA with Sidak post hoc comparisons. Results: 8 intact female dogs were included and received all 4 treatments in a random sequence. All dogs tolerated the AAT procedure well. Clonidine significantly delayed GE, increasing time to peak concentration from 80.6 ± 15.9 minutes to 187.5 ± 53.8 minutes. Neither metoclopramide nor azithromycin reversed this delay. Conclusions: The AAT identified delayed liquid-phase GE following clonidine administration. However, at the investigated dosages, metoclopramide and azithromycin did not mitigate clonidine-induced delayed GE. Clinical Relevance: The AAT shows potential as a clinical tool for identifying delayed GE of liquids, particularly in critically ill or postoperative patients.

Environmentally persistent free radicals (EPFRs) are stable free radicals formed on particulate matter (PM) through processes such as combustion and pyrolysis. These free radicals are generated on transition metal oxide surfaces in the presence of aromatic precursors. Exposure to EPFRs occurs primarily via inhalation of PM deriving from combustion, traffic, industrial activities, and both indoor and outdoor burning. Other environmental factors that might generate EPFRs are radon, electronic and tobacco cigarettes. EPFRs exhibit unexpectedly long half-lives, ranging from several weeks to, in some cases, several years. EPFRs may be carbon-centered, oxygen-centered or mixed, identified by g-values exhibited in electron paramagnetic resonance analysis. The radicals undergo redox cycling within aqueous solutions and in biological tissues/fluids triggering production of reactive oxygen species (ROS), comprised primarily of hydroxyl, superoxide, and peroxyl radicals. The stability of EPFRs, their association with PM_2.5, and their ability to generate ROS may pose significant concerns for human health. To determine whether there are sufficient data for risk assessment, recent advances were examined in the following important aspects of EPFR research: (1) atmospheric chemistry, (2) human exposures, (3) animal toxicity, and (4) epidemiology. Our review found insufficient epidemiological and exposure studies; however, toxicological data in animals suggested that EPFR inhalation contributes to cardiovascular, respiratory, and metabolic diseases. Although EPFRs are not currently surveyed by a regulatory monitoring system, data indicate their widespread presence in the environment and their potential to initiate/exacerbate diseases.

Peripheral artery disease (PAD) is a disease of both atherosclerotic and thromboembolic pathology, affecting more than 230 million people globally. PAD patients are at an increased risk of thrombotic events and often require lifelong antithrombotic therapy. Thromboembolism can lead to complete occlusion of affected arteries and put patients at risk for critical limb threatening ischemia (CTLI). PAD blockages are cleared using drug-eluting stents (DES) and drug-coated balloons (DCB). However, PAD treatment below the knee (BTK) presents unique challenges. While DCB are frequently used to treat BTK disease, no DCB has gained FDA approval for this indication. However, innovation in the field has produced drug delivery systems and formulations that may yet enhance the effectiveness of these therapies. In this review, we will provide a brief overview of the pathological mechanisms associated with PAD and review the materials and drugs frequently used in DCBs with an emphasis on excipients and drug carriers. Finally, we will highlight emerging devices undergoing clinical trials to treat BTK disease and how they differ from their predecessors.

Particulate matter containing environmentally persistent free radicals (EPFRs) is formed when organic pollutants are incompletely burned and adsorb to the surface of particles containing redox-active metals. Our prior studies showed that in mice, EPFR inhalation impaired vascular relaxation in a dose- and endothelium-dependent manner. We also observed that activation of the aryl hydrocarbon receptor (AhR) in the alveolar type-II (AT-II) cells that form the air-blood interface stimulates the release of systemic factors that promote endothelial dysfunction in vessels peripheral to the lung. AhR is a recognized regulator of microRNA (miRNA) biogenesis, and miRNA control diverse signaling pathways. We thus hypothesized that systemic EPFR-induced vascular endothelial dysfunction is initiated via AhR activation in AT-II cells, resulting in a systemic release of miRNA. Using a combustion reactor, we generated EPFR of two free radical concentrations—EPFR_lo (10^16–17 radicals/g particles) and EPFR (10^18–19 radicals/g)—and exposed mice by inhalation. EFPR inhalation resulted in changes in a distinct array of miRNA in the plasma, and these miRNAs are linked to multiple systemic effects, including cardiovascular diseases and dysregulation of cellular and molecular pathways associated with cardiovascular dysfunction. We identified 17 miRNA in plasma that were altered dependent upon both AhR activation in AT-II cells and ~ 280 ug/m³ EPFR exposure. Using Ingenuity Pathway Analysis, we found that 5 of these miRNAs have roles in modulating endothelin-1 and endothelial nitric oxide signaling, known regulators of endothelial function. Furthermore, EPFR exposure reduced the expression of lung adherens and gap junction proteins in control mice but not AT-II-AhR deficient mice, and reductions in barrier function may facilitate miRNA release from the lungs. In summary, our findings support that miRNA may be systemic mediators promoting endothelial dysfunction mediated via EPFR-induced AhR activation at the air-blood interface. Graphical Abstract

4,4′‐Diaminodiphenylmethane (DAPM) is an aromatic amine used in the industrial synthesis of polyurethane. In rats, acute DAPM exposure induces biliary epithelial cell injury in the liver, but subchronic exposure promotes a female‐specific pulmonary arterial hypertension (PAH). PAH in humans is four times more prevalent in women than men. To shed light on mechanisms explaining the female selectivity of PAH in humans, we examined molecular pathways underlying DAPM‐induced PAH in female rats. Intersections between DAPM‐mediated hepatic injury and DAPM‐induced PAH were also interrogated. Intact compared to ovariectomized female rats were gavaged once weekly for 12 weeks with DAPM or vehicle. Morphometric analysis in lung sections was used to quantify PAH pathology. mRNA from liver were assessed for DAPM‐induced alterations in genes associated with aryl hydrocarbon receptor, estrogen response, and endothelin‐1 signaling. mRNA from pulmonary arteries were subjected to transcript profiling, and pathways associated with differentially expressed genes were mapped. First, DAPM‐induced PAH was exacerbated by ovariectomy. Although DAPM‐mediated liver injury per se was not correlated with its induction of PAH, increases in levels of the potent vasoconstrictor endothelin‐1 were exacerbated by ovariectomy and were correlated with increased expression of Edn1 in the liver. In pulmonary arteries, transcript profiling revealed that DAPM and ovariectomy interacted to dysregulate estrogen receptor, VEGF, PI3K/AKT, endothelin‐1, glucocorticoid receptor, IL‐17A, and idiopathic pulmonary fibrosis signaling. One of the most dysregulated genes associated with both DAPM and estrogen status was Serpine1.

Particulate matter (PM) containing environmentally persistent free radicals (EPFR) is formed by the incomplete combustion of organic wastes, resulting in the chemisorption of pollutants to the surface of PM containing redox-active transition metals. In prior studies in mice, EPFR inhalation impaired endothelium-dependent vasodilation. These findings were associated with aryl hydrocarbon receptor (AhR) activation in the alveolar type-II (AT-II) cells that form the air-blood interface in the lung. We thus hypothesized that AhR activation in AT-II cells promotes the systemic release of mediators that promote endothelium dysfunction peripheral to the lung. To test our hypothesis, we knocked down AhR in AT-II cells of male and female mice and exposed them to 280 µg/m3 EPFR lo (2.7e + 16 radicals/g) or EPFR (5.5e + 17 radicals/g) compared with filtered air for 4 h/day for 1 day or 5 days. AT-II-AhR activation-induced EPFR-mediated endothelial dysfunction, reducing endothelium-dependent vasorelaxation by 59%, and eNOS expression by 50%. It also increased endothelin-1 mRNA levels in the lungs and peptide levels in the plasma in a paracrine fashion, along with soluble vascular cell adhesion molecule-1 and iNOS mRNA expression, possibly via NF-kB activation. Finally, AhR-dependent increases in antioxidant response signaling, coupled to increased levels of 3-nitrotyrosine in the lungs of EPFR-exposed littermate control but not AT-II AhR KO mice suggested that ATII-specific AhR activation promotes oxidative and nitrative stress. Thus, AhR activation at the air-blood interface mediates endothelial dysfunction observed peripheral to the lung, potentially via release of systemic mediators.

Peripheral artery disease (PAD) is a systemic vascular disease of the legs that results in a blockage of blood flow from the heart to the lower extremities. Now one of the most common causes of mortality in the U.S., the first line of therapy for PAD is to mechanically open the blockages using balloon angioplasty. Coating the balloons with antiproliferative agents can potentially reduce vessel re-narrowing, or restenosis after surgical intervention, but current drug-coated balloons releasing chemotherapy agents like paclitaxel have in some cases shown increased mortality long-term. Our aim was to design a novel drug-coated balloon using a polymeric nanodelivery system for a sustained release of polyphenols that reduce restenosis but with reduced toxicity compared to chemotherapy agents. Poly (lactic-co-glycolic acid) (PLGA) nanoparticles with entrapped quercetin, a dimethoxy quercetin (rhamnazin), as well as quercetin covalently attached to PLGA, were developed. Balloon catheters were coated with polymeric nanoparticles using an ultrasonic method, and nanoparticle characteristics, drug loading, coating uniformity and drug release were determined. The adhesion of nanoparticles to vascular smooth muscle cells and the antiproliferative effect of nano-delivered polyphenols were also assessed. Of the nanoparticle systems tested, those with covalently attached quercetin provided the most sustained release over a 6-day period. Although these particles adhered to cells to a smaller extent compared to other nanoparticle formulations, their attachment was resistant to washing. These particles also exhibited the greatest anti-proliferative effect. In addition, their attachment was not altered when the cells were grown in calcifying conditions, and in PAD tissue calcification is typically a condition that impedes drug delivery. Moreover, the ultrasonic coating method generated a uniform balloon coating. The polymeric nanoparticle system with covalently attached quercetin developed herein is thus proposed as a promising platform to reduce restenosis post-angioplasty.

Peripheral artery disease (PAD) is a systemic vascular disease of the legs that results in a blockage of blood flow from the heart to the lower extremities. Now one of the most common causes of mortality in the U.S., the first line of therapy for PAD is to mechanically open the blockages using balloon angioplasty. Coating the balloons with antiproliferative agents can potentially reduce vessel re-narrowing, or restenosis after surgical intervention, but current drug-coated balloons releasing chemotherapy agents like paclitaxel have in some cases shown increased mortality long-term. Our aim was to design a novel drug-coated balloon using a polymeric nanodelivery system for a sustained release of polyphenols that reduce restenosis but with reduced toxicity compared to chemotherapy agents. Poly (lactic-co-glycolic acid) (PLGA) nanoparticles with entrapped quercetin, a dimethoxy quercetin (rhamnazin), as well as quercetin conjugated to PLGA, were developed. Balloon catheters were coated with polymeric nanoparticles using an ultrasonic method, and nanoparticle characteristics, drug loading, coating uniformity and drug release were determined. The adhesion of nanoparticles to vascular smooth muscle cells and the antiproliferative effect of nano-delivered polyphenols were also assessed. Of the nanoparticle systems tested, those with covalently attached quercetin provided the most sustained release over a 6-day period. Although these particles adhered to cells to a smaller extent compared to other nanoparticle formulations, their attachment was resistant to washing. These particles also exhibited the greatest anti-proliferative effect. In addition, their attachment was not altered when the cells were grown in calcifying conditions, and in PAD tissue calcification is typically a condition that impedes drug delivery. Moreover, the ultrasonic coating method generated a uniform balloon coating. The polymeric nanoparticle system with covalently attached quercetin developed herein is thus proposed as a promising platform to reduce restenosis post-angioplasty.

Particulate matter (PM) resulting from the combustion of organic matter is known to contribute to cardiopulmonary disease. Despite hypotheses that cardiovascular dysfunction occurring after PM exposures is secondary to lung or systemic inflammation, these studies investigating exposures to PM-containing environmentally persistent free radicals (EPFRs) demonstrate that cardiovascular dysfunction precedes pulmonary inflammation. The cardiopulmonary health consequences of EPFRs have yet to be thoroughly evaluated, especially in healthy, adult mice. Our data suggest the vasculature as a direct target of PM exposure, and our studies aimed to elucidate the mechanisms contributing to EPFR-induced vascular dysfunction.

Toxicological Sciences, Volume 172, Issue 2, December 2019, Pages 445–456, https://doi.org/10.1093/toxsci/kfz203