Distribution of Antibiotic Resistance in a Mixed-Use Watershed and the Impact of Wastewater Treatment Plants on Antibiotic Resistance in Surface Water

The aquatic environment has been recognized as a source of antibiotic resistance (AR) that factors into the One Health approach to combat AR. To provide much needed data on AR in the environment, a comprehensive survey of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antibiotic residues was conducted in a mixed-use watershed and wastewater treatment plants (WWTPs) within the watershed to evaluate these contaminants in surface water. A culture-based approach was used to determine prevalence and diversity of ARB in surface water. Low levels of AR Salmonella (9.6%) and Escherichia coli (6.5%) were detected, while all Enterococcus were resistant to at least one tested antibiotic. Fewer than 20% of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (17.3%) and carbapenem-resistant Enterobacteriaceae (CRE) (7.7%) were recovered. Six ARGs were detected using qPCR, primarily the erythromycin-resistance gene, ermB. Of the 26 antibiotics measured, almost all water samples (98.7%) had detectable levels of antibiotics. Analysis of wastewater samples from three WWTPs showed that WWTPs did not completely remove AR contaminants. ARGs and antibiotics were detected in all the WWTP effluent discharges, indicating that WWTPs are the source of AR contaminants in receiving water. However, no significant difference in ARGs and antibiotics between the upstream and downstream water suggests that there are other sources of AR contamination. The widespread occurrence and abundance of medically important antibiotics, bacteria resistant to antibiotics used for human and veterinary purposes, and the genes associated with resistance to these antibiotics, may potentially pose risks to the local populations exposed to these water sources.

Involvement of extracellular vesicles in the progression, diagnosis, treatment, and prevention of whole-body ionizing radiation-induced immune dysfunction

Acute radiation syndrome (ARS) develops after exposure to high doses of ionizing radiation and features immune suppression and organ failure. Currently, there are no diagnostics to identify the occurrence or severity of exposure and there are limited treatments and preventative strategies to mitigate ARS. Extracellular vesicles (EVs) are mediators of intercellular communication that contribute to immune dysfunction across many diseases. We investigated if EV cargo can identify whole body irradiation (WBIR) exposure and if EVs promote ARS immune dysfunction. We hypothesized that beneficial EVs derived from mesenchymal stem cells (MSC-EVs) would blunt ARS immune dysfunction and might serve as prophylactic radioprotectants. Mice received WBIR (2 or 9 Gy) with assessment of EVs at 3 and 7 days after exposure. LC-MS/MS proteomic analysis of WBIR-EVs found dose-related changes as well as candidate proteins that were increased with both doses and timepoints (34 total) such as Thromboxane-A Synthase and lymphocyte cytosolic protein 2. Suprabasin and Sarcalumenin were increased only after 9 Gy suggesting these proteins may indicate high dose/lethal exposure. Analysis of EV miRNAs identified miR-376 and miR-136, which were increased up to 200- and 60-fold respectively by both doses of WBIR and select miRNAs such as miR-1839 and miR-664 were increased only with 9 Gy. WBIR-EVs (9 Gy) were biologically active and blunted immune responses to LPS in RAW264.7 macrophages, inhibiting canonical signaling pathways associated with wound healing and phagosome formation. When given 3 days after exposure, MSC-EVs slightly modified immune gene expression changes in the spleens of mice in response to WBIR and in a combined radiation plus burn injury exposure (RCI). MSC-EVs normalized the expression of certain key immune genes such as NFκBia and Cxcr4 (WBIR), Map4k1, Ccr9 and Cxcl12 (RCI) and lowered plasma TNFα cytokine levels after RCI. When given prophylactically (24 and 3 hours before exposure), MSC-EVs prolonged survival to the 9 Gy lethal exposure. Thus, EVs are important participants in ARS. EV cargo might be used to diagnose WBIR exposure, and MSC-EVs might serve as radioprotectants to blunt the impact of toxic radiation exposure.

NUCLEAR FACTOR-ERYTHROID-2-RELATED FACTOR REGULATES SYSTEMIC AND PULMONARY BARRIER FUNCTION AND IMMUNE PROGRAMMING AFTER BURN AND INHALATION INJURY

ABSTRACT

Major burn injury is associated with systemic hyperinflammatory and oxidative stresses that encompass the wound, vascular, and pulmonary systems that contribute to complications and poor outcomes. These stresses are exacerbated if there is a combined burn and inhalation (B+I) injury, which leads to increases in morbidity and mortality. Nuclear factor-erythroid-2-related factor (NRF2) is a transcription factor that functions to maintain homeostasis during stress, in part by modulating inflammation and oxidative injury. We hypothesized that the NRF2-mediated homeostasis after burn alone and combined B-I injury is insufficient, but that pharmacological activation of the NRF2 pathway has the potential to reduce/reverse acute hyper inflammatory responses. We found that, after burn and B+I injury, Nrf2 -/- mice have higher mortality and exhibit greater pulmonary edema, vascular permeability, and exacerbated pulmonary and systemic proinflammatory responses compared with injured wild-type (WT) controls. Transcriptome analysis of lung tissue revealed specific Nrf2 -dependent dysregulated immune pathways after injury. In WT mice, we observed that B+I injury induces cytosolic, but not nuclear, accumulation of NRF2 protein in the lung microenvironment compared with sham-injured controls. Bardoxolone methyl (CDDO-Me)-containing microparticles (CDDO-MPs) were developed that allow for dilution in saline and stable release of CDDO-Me. When delivered intraperitoneally into mice 1 hour after B+I injury, CDDO-MPs significantly reduced mortality and cytokine dysfunction compared with untreated B-I animals. These data implicate the role of NRF2 regulation of pulmonary and systemic immune dysfunction after burn and B+I injury, and also a deficiency in controlling immune dysregulation. Selectively activating the NRF2 pathway may improve clinical outcomes in burn and B+I patients.

EXTRACELLULAR VESICLES AS REGULATORS OF IMMUNE FUNCTION IN TRAUMATIC INJURIES AND SEPSIS

ABSTRACT

Despite advancements in critical care and resuscitation, traumatic injuries are one of the leading causes of death around the world and can bring about long-term disabilities in survivors. One of the primary causes of death for trauma patients are secondary phase complications that can develop weeks or months after the initial insult. These secondary complications typically occur because of systemic immune dysfunction that develops in response to injury, which can lead to immunosuppression, coagulopathy, multiple organ failure, unregulated inflammation, and potentially sepsis in patients. Recently, extracellular vesicles (EVs) have been identified as mediators of these processes because their levels are increased in circulation after traumatic injury and they encapsulate cargo that can aggravate these secondary complications. In this review, we will discuss the role of EVs in the posttrauma pathologies that arise after burn injuries, trauma to the central nervous system, and infection. In addition, we will examine the use of EVs as biomarkers for predicting late-stage trauma outcomes and as therapeutics for reversing the pathological processes that develop after trauma. Overall, EVs have emerged as critical mediators of trauma-associated pathology and their use as a therapeutic agent represents an exciting new field of biomedicine.

42 The Overt Pulmonary and Systemic Pro-inflammatory Response After Burn and Inhalation Injury Is Mtor Dependent

Introduction

Severe burn injury can lead to local and systemic activation of the innate immune system which can cause a dysfunctional and overt pro-inflammatory response, resulting in inflammatory complications and organ dysfunction. If there is an inhalation injury concomitant with burn, patients have a 3.6 times higher mortality rate and greater than 70% chance of developing secondary respiratory complications. Previous work has shown that the Mechanistic/ Mammalian Target of Rapamycin (mTOR) pathway is involved in signaling neutrophil activity in burn patients. Antagonists of mTOR stimulation represent possible immunomodulatory therapies. However, it is unclear if mTOR plays a role in the pulmonary distress seen after combined burn and smoke inhalation (B+I) injury. The goals of this study were to 1) characterize a novel mouse model of combined B+I injury and 2) investigate the role of mTOR in the pro-inflammatory response after B+I injury.

Methods

We built upon our pre-established 20% total body surface area cutaneous burn mouse model by adding smoke inhalation injury and treating mice with rapamycin, a mTOR-specific inhibitor. In brief, mice were anesthetized before receiving controlled B+I, burn only, or sham injury. After resuscitation, they were given morphinated water for 24 hours before euthanasia and tissue collection. RNA and whole cells were extracted from lung and spleen tissue for analysis by Nanostring and Flow Cytometry, respectively. Fluid within the lung (bronchoalveolar lavage, BAL) and peripheral blood plasma were collected for pro-inflammatory cytokine quantification via magnetic bead multiplex assays.

Results

Wildtype female C57BL/6 mice that underwent B+I injury exhibited elevated levels of protein, macrophages, and neutrophils in the lung cavity compared to burn alone. In addition, 29 genes were significantly differentially expressed in the lung tissue after B+I, suggesting that inhalation elicits a unique response when compared to burn alone. In the peripheral blood, B+I mice have a >4 fold increase in IL6 and 3 fold increase in MCP-1 pro-inflammatory cytokine levels. When we examined the role of mTOR in B+I injury, we found that pre-emptive rapamycin treatment leads to a reduction in peripheral blood pro-inflammatory cytokine levels, namely MCP1, TNFa, IL10, and IL2, and an increase in pro-inflammatory cytokine IL2 in the lung cavity. Rapamycin significantly affected expression levels of 46 genes in the lung and 36 genes in the spleen, indicating an mTOR-dependent response to inhalation injury.

Conclusions

In conclusion, these data describe a valuable mouse model of B+I with inhalation-specific immune phenotypes and implicate mTOR in the inhalation-induced hyper pro-inflammatory response.

46 Bardoxolone-methyl Microparticles Ameliorate Immune Dysfunction Following Burn and Inhalation Injury Through the NRF2/KEAP1 Axis

Introduction

Severe burn injury leads to many systemic stresses that can seriously impact multiple systems throughout the body. These stresses are further exacerbated if there is a combined burn and inhalation injury, which leads to increased morbidity and mortality for many patients. Combined burn and inhalation injury causes an intense systemic inflammatory response and activation of the innate immune system which can lead to inflammatory complications, such as systemic inflammatory response syndrome and multiple organ failure. Nuclear Factor-Erythroid-2-Related Factor (NRF2) is a transcription factor that acts to downregulate overt damaging pro-inflammatory and oxidative responses and maintain immune homeostasis. This transcription factor remains bound to Kelch-like ECH-associated protein 1 (KEAP1) in the cytoplasm. Under oxidative stress, NRF2 dissociates from KEAP1 and translocates to the nucleus where it facilitates the transcription of anti-inflammatory and antioxidant genes. We hypothesized that NRF2 is a key regulator after burn and inhalation injury, and activation of NRF2 can limit the severity of burn and inhalation injury.

Methods

To test this, we have developed a mouse model of combined cutaneous burn and woodsmoke inhalation injury. After burn and inhalation injury, we found that NRF2^-/- knockout mice have higher mortality compared to wild-type (WT) mice and suffer from increased vascular permeability and lung edema, suggesting that this transcription factor is important for controlling morbidity and mortality. In WT mice, NRF2 is activated following burn and inhalation injury, however, based on immunohistochemical staining, it is not sufficiently induced following this insult since it remains in the cytoplasm and is unable to transcribe anti-inflammatory genes. Therefore, we treated WT mice with an intraperitoneal injection of bardoxolone-methyl microparticles, a NRF2 activator that separates KEAP1 from NRF2 in the cytoplasm, immediately after burn and inhalation injury in WT mice

Results

We observed significant decreases in mortality as well as reduced concentrations of certain pro-inflammatory cytokines in the blood and bronchoalveolar-lavage fluid of these mice. In the lungs of these mice, there was an upregulation in numerous pathways involved in the management of inflammation and immune response compared to mice that did not receive bardoxolone-methyl microparticles.

Conclusions

In conclusion, treatment with bardoxolone-methyl microparticles immediately after burn and inhalation injury might be effective for reducing the severity of the inflammatory response and limiting inflammatory complications.

Using metabolomic profiling to inform use of surrogate species in ecological risk assessment practices

The U.S. EPA frequently uses avian or fish toxicity data to set protective standards for amphibians in ecological risk assessments. However, this approach does not always adequately represent aquatic-dwelling and terrestrial-phase amphibian exposure data. For instance, it is accepted that early life stage tests for fish are typically sensitive enough to protect larval amphibians, however, metamorphosis from tadpole to a terrestrial-phase adult relies on endocrine cues that are less prevalent in fish but essential for amphibian life stage transitions. These differences suggest that more robust approaches are needed to adequately elucidate the impacts of pesticide exposure in amphibians across critical life stages. Therefore, in the current study, methodology is presented that can be applied to link the perturbations in the metabolomic response of larval zebrafish (Danio rerio), a surrogate species frequently used in ecotoxicological studies, to those of African clawed frog (Xenopus laevis) tadpoles following exposure to three high-use pesticides, bifenthrin, chlorothalonil, or trifluralin. Generally, D. rerio exhibited greater metabolic perturbations in both number and magnitude across the pesticide exposures as opposed to X. laevis. This suggests that screening ecological risk assessment surrogate toxicity data would sufficiently protect amphibians at the single life stage studied but care needs to be taken to understand the suite of metabolic requirements of each developing species. Ultimately, methodology presented, and data gathered herein will help inform the applicability of metabolomic profiling in establishing the risk pesticide exposure poses to amphibians and potentially other non-target species.

Integrated Omic Analyses Identify Pathways and Transcriptomic Regulators Associated with Chemical Alterations of in Vitro Neural Network Formation

Development of in vitro new approach methodologies (NAMs) has been driven by the need for developmental neurotoxicity (DNT) hazard data on thousands of chemicals. The network formation assay (NFA) characterizes DNT hazard based on changes in network formation but provides no mechanistic information. This study investigated nervous system signaling pathways and upstream physiological regulators underlying chemically-induced neural network dysfunction. Rat primary cortical neural networks grown on microelectrode arrays were exposed for 12 days in vitro (DIV) to cytosine arabinoside (CA), 5 fluorouracil (5FU), domoic acid (DA), cypermethrin (CM), deltamethrin (DM), or haloperidol (HP) as these exposures altered network formation in previous studies. RNA-seq from cells and GC/MS analysis of media extracts collected on DIV 12 provided gene expression and metabolomic identification, respectively. The integration of differentially expressed genes and metabolites for each neurotoxicant was analyzed using Ingenuity Pathway Analysis (IPA). All six compounds altered gene expression that linked to developmental disorders and neurological diseases. Other enriched canonical pathways overlapped among compounds of the same class; for example, genes and metabolites altered by both CA and 5FU exposures are enriched in axonal guidance pathways. Integrated analysis of upstream regulators was heterogeneous across compounds, but identified several transcriptomic regulators including CREB1, SOX2, NOTCH1, and PRODH. These results demonstrate that changes in network formation are accompanied by transcriptomic and metabolomic changes and that different classes of compounds produce differing responses. This approach can enhance information obtained from NAMs and contribute to the identification and development of adverse outcome pathways (AOPs) associated with DNT.

Cross-Taxa Distinctions in Mechanisms of Developmental Effects for Aquatic Species Exposed to Trifluralin

Standard ecological risk assessment practices often rely on larval and juvenile fish toxicity data as representative of the amphibian aquatic phase. Empirical evidence suggests that endpoints measured in fish early life stage tests are often sufficient to protect larval amphibians. However, the process of amphibian metamorphosis relies on endocrine cues that affect development and morphological restructuring and are not represented by these test endpoints. The present study compares developmental endpoints for zebrafish (Danio rerio) and the African clawed frog (Xenopus laevis), 2 standard test species, exposed to the herbicide trifluralin throughout the larval period. Danio rerio were more sensitive and demonstrated a reduction in growth measurements with increasing trifluralin exposure. Size of X. laevis at metamorphosis was not correlated with exposure concentration; however, time to metamorphosis was delayed relative to trifluralin concentration. Gene expression patterns indicate discrepancies in response by D. rerio and X. laevis, and dose-dependent metabolic activity suggests that trifluralin exposure perturbed biological pathways differently within the 2 species. Although many metabolites were correlated with exposure concentration in D. rerio, nontargeted hepatic metabolomics identified a subset of metabolites that exhibited a nonmonotonic response to trifluralin exposure in X. laevis. Linking taxonomic distinctions in cellular-level response with ecologically relevant endpoints will refine assumptions used in interspecies extrapolation of standard test effects and improve assessment of sublethal impacts on amphibian populations. Environ Toxicol Chem 2020;39:1797-1812. Published 2020. This article is a US government work and is in the public domain in the USA.