Trichloroethylene perturbs HNF4a expression and activity in the developing chick heart

Trichloroethylene exposure, multi-organ injury, and potential mechanisms: A narrative review

Trichloroethylene (TCE) is a common environmental pollutant and industrial chemical that has been associated with adverse health effects, especially on organ systems. The purpose of this review is to summarize the current findings on organ system damage caused by TCE exposure and the underlying mechanisms involved. Numerous studies have shown that TCE exposure may cause damage to multiple organ systems, mainly the skin, liver, kidney, and circulatory system. The mechanisms leading to TCE-induced organ system damage are complex and diverse. TCE is metabolized in vivo to reactive intermediates, through which TCE can induce oxidative stress, interfere with cell signaling pathways, and promote inflammatory responses. In addition, studies have shown that TCE interferes with DNA repair mechanisms, leading to genotoxicity and potentially carcinogenic effects. This review highlights the importance of understanding the deleterious effects of TCE exposure on organ systems and provides insights into the underlying mechanisms involved. Further research is needed to elucidate the full range of organ system damage caused by TCE and to develop effective prevention and treatment strategies.

Corticosteroid-induced bradycardia in multiple sclerosis and maturity-onset diabetes of the young due to hepatocyte nuclear factor 4-alpha mutation: A case report

BACKGROUND

Intravenous steroid pulse therapy is the treatment of choice for acute exacerbation of multiple sclerosis (MS). Although steroid administration is generally well-tolerated, cases of cardiac arrhythmia have been reported. Herein, we describe a young woman who developed marked sinus bradycardia and T-wave abnormalities after corticosteroid administration. We also present plausible explanations for the abnormalities observed in this patient.

CASE SUMMARY

An 18-year-old woman experienced vertiginous dizziness and binocular diplopia 1 wk prior to admission. Neurological examination revealed left internuclear ophthalmoplegia with left peripheral-type facial palsy. The initial laboratory results were consistent with those of type 2 diabetes. Brain magnetic resonance imaging revealed multifocal, non-enhancing, symptomatic lesions and multiple enhancing lesions. She was diagnosed with MS and maturity-onset diabetes of the young. Intravenous methylprednisolone was administered. On day 5 after methylprednisolone infusion, marked bradycardia with T-wave abnormalities were observed. Genetic evaluation to elucidate the underlying conditions revealed a hepatocyte nuclear factor 4-alpha (HNF4A) gene mutation. Steroid treatment was discontinued under suspicion of corticosteroid-induced bradycardia. Her electrocardiogram changes returned to normal without complications two days after steroid discontinuation.

CONCLUSION

Corticosteroid-induced bradycardia may have a significant clinical impact, especially in patients with comorbidities, such as HNF4A mutations.

Membrane Attack Complex C5b-9 Promotes Renal Tubular Epithelial Cell Pyroptosis in Trichloroethylene-Sensitized Mice

Trichloroethylene (TCE), a commonly used organic solvent, is known to cause trichloroethylene hypersensitivity syndrome (THS), also called occupational medicamentosa-like dermatitis due to TCE (OMDT) in China. OMDT patients presented with severe inflammatory kidney damage, and we have previously shown that the renal damage is related to the terminal complement complex C5b-9. Here, we sought to determine whether C5b-9 participated in TCE-induced immune kidney injury by promoting pyroptosis, a new form of programed cell death linked to inflammatory response, with underlying molecular mechanisms involving the NLRP3 inflammasome. A BALB/c mouse-based model of OMDT was established by dermal TCE sensitization in the presence or absence of C5b-9 inhibitor (sCD59-Cys, 25μg/mouse) and NLRP3 antagonist (MCC950, 10 mg/kg). Kidney histopathology, renal function, expression of inflammatory mediators and the pyroptosis executive protein gasdermin D (GSDMD), and the activation of pyroptosis canonical NLRP3/caspase-1 pathway were examined in the mouse model. Renal tubular damage was observed in TCE-sensitized mice. GSDMD was mainly expressed on renal tubular epithelial cells (RTECs). The caspase-1-dependent canonical pathway of pyroptosis was activated in TCE-induced renal damage. Pharmacological inhibition of C5b-9 could restrain the caspase-1-dependent canonical pathway and rescued the renal tubular damage. Taken together, our results demonstrated that complement C5b-9 plays a central role in TCE-induced immune kidney damage, and the underlying mechanisms involve NLRP3-mediated pyroptosis.

Mechanosensitive Pathways in Heart Development: Findings from Chick Embryo Studies

The heart is the first organ that starts to function in a developing embryo. It continues to undergo dramatic morphological changes while pumping blood to the rest of the body. Genetic regulation of heart development is partly governed by hemodynamics. Chick embryo is a major animal model that has been used extensively in cardiogenesis research. To reveal mechanosensitive pathways, a variety of surgical interferences and chemical treatments can be applied to the chick embryo to manipulate the blood flow. Such manipulations alter expressions of mechanosensitive genes which may anticipate induction of morphological changes in the developing heart. This paper aims to present different approaches for generating clinically relevant disturbed hemodynamics conditions using this embryonic chick model and to summarize identified mechanosensitive genes using the model, providing insights into embryonic origins of congenital heart defects.

Classic and Novel Sex Hormone Binding Globulin Effects on the Cardiovascular System in Men

In men, 70% of circulating testosterone binds with high affinity to plasma sex hormone binding globulin (SHBG), which determines its bioavailability in their target cells. In recent years, a growing body of evidence has shown that circulating SHBG not only is a passive carrier for steroid hormones but also actively regulates testosterone signaling through putative plasma membrane receptors and by local expression of androgen-binding proteins apparently to reach local elevated testosterone concentrations in specific androgen target tissues. Circulating SHBG levels are influenced by metabolic and hormonal factors, and they are reduced in obesity and insulin resistance, suggesting that SHBG may have a broader clinical utility in assessing the risk for cardiovascular diseases. Importantly, plasma SHBG levels are strongly correlated with testosterone concentrations, and in men, low testosterone levels are associated with an adverse cardiometabolic profile. Although obesity and insulin resistance are associated with an increased incidence of cardiovascular disease, whether they lead to abnormal expression of circulating SHBG or its interaction with androgen signaling remains to be elucidated. SHBG is produced mainly in the liver, but it can also be expressed in several tissues including the brain, fat tissue, and myocardium. Expression of SHBG is controlled by peroxisome proliferator-activated receptor γ (PPARγ) and AMP-activated protein kinase (AMPK). AMPK/PPAR interaction is critical to regulate hepatocyte nuclear factor-4 (HNF4), a prerequisite for SHBG upregulation. In cardiomyocytes, testosterone activates AMPK and PPARs. Therefore, the description of local expression of cardiac SHBG and its circulating levels may shed new light to explain physiological and adverse cardiometabolic roles of androgens in different tissues. According to emerging clinical evidence, here, we will discuss the potential mechanisms with cardioprotective effects and SHBG levels to be used as an early metabolic and cardiovascular biomarker in men.

Matrix factorization and transfer learning uncover regulatory biology across multiple single-cell ATAC-seq data sets

While the methods available for single-cell ATAC-seq analysis are well optimized for clustering cell types, the question of how to integrate multiple scATAC-seq data sets and/or sequencing modalities is still open. We present an analysis framework that enables such integration across scATAC-seq data sets by applying the CoGAPS Matrix Factorization algorithm and the projectR transfer learning program to identify common regulatory patterns across scATAC-seq data sets. We additionally integrate our analysis with scRNA-seq data to identify orthogonal evidence for transcriptional regulators predicted by scATAC-seq analysis. Using publicly available scATAC-seq data, we find patterns that accurately characterize cell types both within and across data sets. Furthermore, we demonstrate that these patterns are both consistent with current biological understanding and reflective of novel regulatory biology.

Systematic evaluation of mechanistic data in assessing in utero exposures to trichloroethylene and development of congenital heart defects

The hypothesis that in utero exposures to low levels of trichloroethylene (TCE) may increase the risk of congenital heart defects (CHDs) in offspring remains a subject of substantial controversy within the scientific community due primarily to the reliance on an inconsistent and unreproducible experimental study in rats. To build on previous assessments that have primarily focused on epidemiological and experimental animal studies in developing conclusions, the objective of the current study is to conduct a systematic evaluation of mechanistic data related to in utero exposures to TCE and the development of CHDs. The evidence base was heterogeneous; 79 mechanistic datasets were identified, characterizing endpoints which ranged from molecular to organismal responses in seven species, involving both in vivo and in vitro study designs in mammalian and non-mammalian models. Of these, 24 datasets were considered reliable following critical appraisal using a study quality tool that employs metrics specific to the study type. Subsequent synthesis and integration demonstrated that the available mechanistic data: 1) did not support the potential for CHD hazard in humans, 2) did not support the biological plausibility of a response in humans based on organization via a putative adverse outcome pathway for valvulo-septal cardiac defects, and 3) were not suitable for serving as candidate studies in risk assessment. Findings supportive of an association were generally limited to in ovo chicken studies, in which TCE was administered in high concentration solutions via direct injection. Results of these in ovo studies were difficult to interpret for human health risk assessment given the lack of generalizability of the study models (including dose relevance, species-specific biological differences, variations in the construct of the study design, etc.). When the mechanistic data are integrated with findings from previous evaluations of human and animal evidence streams, the totality of evidence does not support CHDs as a critical effect in TCE human health risk assessment.

HNF4a transcription is a target of trichloroethylene toxicity in the embryonic mouse heart

In exploration of congenital heart defects produced by TCE, Hepatocyte Nuclear Factor 4 alpha (HNF4a) transcriptional activity was identified as a central component. TCE exposure altered gene transcription in the chick heart in a non-monotonic pattern where only low dose exposure inhibited transcription by HNF4a. As the chick embryo is non-placental, we examine here HNF4a as a target of TCE in developing mouse embryos. Benfluorex and Bi6015, published agonist and antagonist, respectively, of HNF4a were compared to low dose TCE exposure. Pregnant mice were exposed to 10 ppb (76 nM) TCE, 5 μM Benfluorex, 5 μM Bi6015, or a combination of Bi6015 and TCE in drinking water. Litters (E12) were collected during a sensitive window in heart development. Embryonic hearts were collected, pooled for extraction of RNA and marker expression was examined by quantitative PCR. Multiple markers, previously identified as sensitive to TCE exposure in chicks or as published targets of HNF4a transcription were significantly affected by Benfluorex, Bi6015 and TCE. Activity of TCE and both HNF4a-specific reagents on transcription argues that HNF4a is a component of TCE cardiotoxicity and likely a proximal target of low dose exposure during development. The effectiveness of these reagents after delivery in maternal drinking water suggests that neither maternal metabolism, nor placental transport is protective of exposure.

Terminal complement complex C5b-9 reduced megalin and cubilin-mediated tubule proteins uptake in a mouse model of trichloroethylene hypersensitivity syndrome

Trichloroethylene (TCE), a commonly used industrial solvent and degreasing agent, is known to cause trichloroethylene hypersensitivity syndrome (THS) with multi-system damage, including skin, liver and kidney. Clinical evidence have shown that the kidney injury occurs in THS and our previous studies suggested that the terminal complement complex C5b-9 deposited in impaired renal tubules induced by TCE with unclear mechanisms. In the present study, we questioned whether activation of the complement system with renal deposition of C5b-9 contributes to TCE-induced kidney injury in THS. We established a BALB/c mouse model of TCE sensitization with or without pretreatment of exogenous CD59, a C5b-9 inhibitory protein. H&E staining, PAS staining, and biochemical detection of urinary proteins were performed to assess renal function. Deposition of C5b-9 and expression of CD59 were evaluated by immunohistochemistry. Sub-lytic effects of C5b-9 in tubular epithelial cells were assessed by lactate dehydrogenase (LDH) cytotoxicity assay. Expression of endocytosis receptors megalin and cubilin on proximal tubules were assessed by immunofluorescence and qRT-PCR. We found that TCE sensitization induced structural and functional changes of renal tubules in mice, associated with the deposition of sub-lytic C5b-9 on proximal tubular epithelial cells. TCE sensitization decreased proximal tubule uptake of filtered proteins and renal expression of megalin and cubilin, phenotypes that were attenuated by pretreatment with exogenous CD59. Overall, our findings reveal a novel mechanism underlying sub-lytic C5b-9 acting on megalin and cubilin, contributes to the renal tubules damage by TCE exposure.