Deficiency of the Transcription Factor NR4A1 Enhances Bacterial Clearance and Prevents Lung Injury During Escherichia Coli Pneumonia

Transcriptome Analysis Reveals Novel Inflammatory Signalings to Glaesserella parasuis Infection

Glaesserella parasuis (GPS) can cause severe systemic inflammation in pigs, resulting in huge economic losses to the pig industry. At present, no effective method is available for the prevention and control of GPS infection. Molecular breeding for disease resistance is imminent, but disease-resistance genes have not been identified. To study the mechanism of systemic acute inflammation caused by GPS, we established three in vitro infection models (3D4/21 cells, PK15 cells, and PAVEC cells) according to its infection path. There was no significant difference in apoptosis among the three kinds of cells after 12 h of continuous GPS stimulation, while inflammatory factors were significantly upregulated. Subsequent transcriptome analysis revealed 1969, 1207, and 3564 differentially expressed genes (DEGs) in 3D4/21 cells, PK15 cells, and PAVEC cells, respectively, after GPS infection. Many of the DEGs were predicted to be associated with inflammatory responses (C3, CD44, etc.); cell proliferation, growth and apoptosis; gene expression; and protein phosphorylation. Key signaling pathways, including S100 family signaling, bacteria and virus recognition, and pathogen-induced cytokine storm signaling, were enriched based on Ingenuity Pathway Analysis (IPA). Furthermore, a total of three putative transmembrane receptors and two putative G-protein-coupled receptors, namely F3, ICAM1, PLAUR, ACKR3, and GPRC5A, were identified by IPA among the three types of cells. ACKR3 and GPRC5A play pivotal roles in bacterial adhesion, invasion, host immune response and inflammatory response through the S100 family signaling pathway. Our findings provide new insights into the pathological mechanisms underlying systemic inflammation caused by GPS infection in pigs, and they lay a foundation for further research on disease-resistance breeding to GPS.

Identification of key genes as potential diagnostic and therapeutic targets for comorbidity of myasthenia gravis and COVID-19

Introduction

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder. Coronavirus disease 2019 (COVID-19) has a significant impact on the health and quality of life of MG patients and may even trigger the onset of MG in some cases. With the worldwide development of the COVID-19 vaccination, several new-onset MG cases and exacerbations following the COVID-19 vaccines have been acknowledged. The potential link between myasthenia gravis (MG) and COVID-19 has prompted the need for further investigation into the underlying molecular mechanism.

Methods and results

The differential expression analysis identified six differentially expressed genes (DEGs) shared by myasthenia gravis (MG) and COVID-19, namely SAMD9, PLEK, GZMB, JUNB, NR4A1, and NR1D1. The relationship between the six common genes and immune cells was investigated in the COVID-19 dataset. The predictive value of the shared genes was assessed and a nomogram was constructed using machine learning algorithms. The regulatory miRNAs, transcription factors and small molecular drugs were predicted, and the molecular docking was carried out by AutoDock.

Discussion

We have identified six common DEGs of MG and COVID-19 and explored their immunological effects and regulatory mechanisms. The result may provide new insights for further mechanism research.

The nuclear receptor subfamily 4 group A1 in human disease

Nuclear receptor 4A1 (NR4A1), a member of the NR4A subfamily, acts as a gene regulator in a wide range of signaling pathways and responses to human diseases. Here, we provide a brief overview of the current functions of NR4A1 in human diseases and the factors involved in its function. A deeper understanding of these mechanisms can potentially improve drug development and disease therapy.

Pterostilbene pre-treatment reduces LPS-induced acute lung injury through activating NR4A1

CONTEXT

Pterostilbene (PTE), a common polyphenol compound, exerts an anti-inflammatory effect in many diseases, including acute lung injury (ALI).

OBJECTIVE

This study explores the potential mechanism of PTE pre-treatment against lipopolysaccharide (LPS)-induced ALI.

MATERIALS AND METHODS

Sixty Sprague-Dawley rats were divided into control, ALI, 10 mg/kg PTE + LPS, 20 mg/kg PTE + LPS, and 40 mg/kg PTE + LPS groups. At 24 h before LPS instillation, PTE was administered orally. At 2 h before LPS instillation, PTE was again administered orally. After 24 h of LPS treatment, the rats were euthanized. The levels of inflammatory cells and inflammatory factors in the bronchoalveolar lavage fluid (BALF), the expression of nuclear receptor subfamily 4 group A member 1 (NR4A1), and the nuclear factor (NF)-κB pathway-related protein levels were detected. NR4A1 agonist was used to further investigate the mechanism of PTE pre-treatment.

RESULTS

After PTE pre-treatment, the LPS induced inflammation was controlled and the survival rate was increased to 100% from 70% after LPS treatment 24 h. For lung injury score, it decreased to 1.5 from 3.5 after treating 40 mg/kg PTE. Compared with the control group, the expression of NR4A1 in the ALI group was decreased by 20-40%. However, the 40 mg/kg PTE pre-treatment increased the NR4A1 expression by 20-40% in the lung tissue. The results obtained with pre-treatment NR4A1 agonist were similar to those obtained by pre-treatment 40 mg/kg PTE.

CONCLUSIONS

PTE pre-treatment might represent an appropriate therapeutic target and strategy for preventing ALI induced by LPS.

NR4A1 Promotes LPS-Induced Acute Lung Injury through Inhibition of Opa1-Mediated Mitochondrial Fusion and Activation of PGAM5-Related Necroptosis

Mitochondrial dysfunction and necroptosis have been perceived as the primary molecular mechanisms underscoring acute lung injury. Meanwhile, nuclear receptor subfamily 4 group A member 1 (NR4A1) is considered a regulator of inflammation-related endothelial injury in lung tissue although the downstream molecular events remain elusive. In this study, we employed NR4A1-/- mice to decipher the role of NR4A1 in the onset and progression of acute lung injury with a focus on mitochondrial damage and necroptosis. Our results demonstrated that NR4A1 was significantly upregulated in lipopolysaccharide- (LPS-) treated lung tissues. Knockout of NR4A1 overtly improved lung tissue morphology, inhibited inflammation, and reduced oxidative stress in LPS-treated lung tissue. A cell signaling study suggested that NR4A1 deletion repressed levels of PGAM5 and attenuated LPS-mediated necroptosis in primary murine alveolar epithelial type II (ATII) cells, the effects of which were mitigated by PGAM5 overexpression. Moreover, LPS-mediated mitochondrial injury including mitochondrial membrane potential collapse and mitochondrial oxidative stress was drastically improved by NR4A1 deletion. Furthermore, NR4A1 deletion preserved mitochondrial homeostasis through activation of Opa1-related mitochondrial fusion. Silencing of Opa1 triggered mitochondrial dysfunction in NR4A1-deleted ATII cells. Taken together, our data identified NR4A1 as a novel regulator of LPS-related acute lung injury through regulation of mitochondrial fusion and necroptosis, indicating therapeutic promises of targeting NR4A1 in the treatment of acute lung injury in clinical practice.

Bladder Exposure to Gardnerella Activates Host Pathways Necessary for Escherichia coli Recurrent UTI

Recurrent urinary tract infections (rUTI) are a costly clinical problem affecting millions of women worldwide each year. The majority of rUTI cases are caused by uropathogenic Escherichia coli (UPEC). Data from humans and mouse models indicate that some instances of rUTI are caused by UPEC emerging from latent reservoirs in the bladder. Women with vaginal dysbiosis, typically characterized by high levels of Gardnerella and other anaerobes, are at increased risk of UTI. Multiple studies have detected Gardnerella in urine collected by transurethral catheterization (to limit vaginal contamination), suggesting that some women experience routine urinary tract exposures. We recently reported that inoculation of Gardnerella into the bladder triggers rUTI from UPEC bladder reservoirs in a mouse model. Here we performed whole bladder RNA-seq to identify host pathways involved in Gardnerella-induced rUTI. We identified a variety host pathways differentially expressed in whole bladders following Gardnerella exposure, such as pathways involved in inflammation/immunity and epithelial turnover. At the gene level, we identified upregulation of Immediate Early (IE) genes, which are induced in various cell types shortly following stimuli like infection and inflammation. One such upregulated IE gene was the orphan nuclear receptor Nur77 (aka Nr4a1). Pilot experiments in Nur77-/- mice suggest that Nur77 is necessary for Gardnerella exposure to trigger rUTI from UPEC reservoirs. These findings demonstrate that bladder gene expression can be impacted by short-lived exposures to urogenital bacteria and warrant future examination of responses in distinct cell types, such as with single cell transcriptomic technologies. The biological validation studies in Nur77-/- mice lay the groundwork for future studies investigating Nur77 and the Immediate Early response in rUTI.

Identification of the Differentially Expressed Genes Involved in the Synergistic Neurotoxicity of an HIV Protease Inhibitor and Methamphetamine

BACKGROUND

The abuse of psychostimulants such as methamphetamine (METH) is common in human immunodeficiency virus (HIV)-infected individuals. Acquired immunodeficiency syndrome (AIDS) patients taking METH and antiretroviral drugs could suffer severe neurologic damage and cognitive impairment.

OBJECTIVE

To reveal the underlying neuropathologic mechanisms of an HIV protease inhibitor (PI) combined with METH, growth-inhibition tests of dopaminergic cells and RNA sequencing were performed.

METHODS

A combination of METH and PI caused more growth inhibition of dopaminergic cells than METH alone or a PI alone. Furthermore, we identified differentially expressed gene (DEG) patterns in the METH vs. untreated cells (1161 genes), PI vs. untreated cells (16 genes), METH-PI vs. PI (3959 genes), and METH-PI vs. METH groups (14 genes).

RESULTS

The DEGs in the METH-PI co-treatment group were verified in the brains of a mouse model using quantitative polymerase chain reaction and were involved mostly in the regulatory functions of cell proliferation and inflammation.

CONCLUSION

Such identification of key regulatory genes could facilitate the study of their neuroprotective potential in the users of METH and PIs.

NR4A1 regulates cerebral ischemia-induced brain injury by regulating neuroinflammation through interaction with NF-κB/p65

Stroke is reported as a leading cause of mortality and disability in the world. Neuroinflammation is significantly induced responding to ischemic stroke, and this process is accompanied with microglial activation. However, the pathogenesis contributing to ischemic stroke remains unclear. NR4A1 (Nur77) is a nuclear receptor that is expressed in macrophages, playing a significant role in regulating inflammatory response. In the present study, we attempted to explore the effects of NR4A1 on ischemic stroke using in vivo and in vitro studies. Results suggested that NR4A1 expression in microglia was markedly increased after cerebral ischemic damage. Then, we found that NR4A1 knockout attenuated ischemia-triggered infarction volume and neuron injury. Also, cognitive impairments were improved in ischemic mice with NR4A1 deficiency, resulting in functional improvements. Moreover, M1 polarization in microglia and neutrophil recruitment was significantly alleviated by NR4A1 deletion, as evidenced by the reduced expression of M1 markers, chemokines, as well as intracellular adhesion molecule-1 (ICAM-1) and myeloperoxidase (MPO) levels. Importantly, we found that NR4A1 could interact with nuclear factor-κB (NF-κB)/p65 based on in vivo and in vitro results. Suppressing p65 activation by the use of its inhibitor clearly reduced the NR4A1 expression, M1 polarization and neutrophil recruitments, while rescued the expression of anti-inflammatory factors in microglia treated with oxygen-glucose deprivation (OGD). Therefore, NR4A1 suppression in microglia restrained neuroinflammation through interacting with NF-κB/p65 to attenuate ischemic stroke.