NR4A Receptors Differentially Regulate NF-κB Signaling in Myeloid Cells

Dysregulation of inflammatory responses is a hallmark of multiple diseases such as atherosclerosis and rheumatoid arthritis. As constitutively active transcription factors, NR4A nuclear receptors function to control the magnitude of inflammatory responses and in chronic inflammatory disease can be protective or pathogenic. Within this study, we demonstrate that TLR4 stimulation using the endotoxin lipopolysaccharide (LPS) rapidly enhances NR4A1–3 expression in human and murine, primary and immortalized myeloid cells with concomitant gene transcription and protein secretion of MIP-3α, a central chemokine implicated in numerous pathologies. Deficiency of NR4A2 and NR4A3 in human and murine myeloid cells reveals that both receptors function as positive regulators of enhanced MIP-3α expression. In contrast, within the same cell types and conditions, altered NR4A activity leads to suppression of LPS-induced MCP-1 gene and protein expression. An equivalent pattern of inflammatory gene regulation is replicated in TNFα-treated myeloid cells. We show that NF-κB is the critical regulator of NR4A1–3, MIP-3α, and MCP-1 during TLR4 stimulation in myeloid cells and highlight a parallel mechanism whereby NR4A activity can repress or enhance NF-κB target gene expression simultaneously. Mechanistic insight reveals that NR4A2 does not require DNA-binding capacity in order to enhance or repress NF-κB target gene expression simultaneously and establishes a role for NF-κB family member Relb as a novel NR4A target gene involved in the positive regulation of MIP-3α. Thus, our data reveal a dynamic role for NR4A receptors concurrently enhancing and repressing NF-κB activity in myeloid cells leading to altered transcription of key inflammatory mediators.

Cancer Risk in Normal Weight Individuals with Metabolic Obesity: A Narrative Review

Obesity represents one of the most significant public health challenges worldwide. Current clinical practice relies on body mass index (BMI) to define the obesity status of an individual, even though the index has long been recognized for its limitations as a measure of body fat. In normal BMI individuals, increased central adiposity has been associated with worse health outcomes, including increased risks of cardiovascular disease and metabolic disorders. The condition leading to these outcomes has been described as metabolic obesity in the normal weight (MONW). More recent evidence suggests that MONW is associated with increased risk of several obesity-related malignancies, including postmenopausal breast, endometrial, colorectal, and liver cancers. In MONW patients, the false reassurance of a normal range BMI can lead to lost opportunities for implementing preventive interventions that may benefit a substantial number of people. A growing body of literature has documented the increased risk profile of MONW individuals and demonstrated practical uses for body composition and biochemical analyses to identify this at-risk population. In this review, we survey the current literature on MONW and cancer, summarize pathophysiology and oncogenic mechanisms, highlight potential strategies for diagnosis and treatment, and suggest directions for future research.

The NR4A agonist, Cytosporone B, attenuates pro-inflammatory mediators in human colorectal cancer tissue ex vivo

Inflammation is a pivotal pathological factor in colorectal cancer (CRC) initiation and progression, and modulating this inflammatory state has the potential to ameliorate disease progression. NR4A receptors have emerged as key regulators of inflammatory pathways that are important in CRC. Here, we have examined the effect of NR4A agonist, Cytosporone B (CsnB), on colorectal tissue integrity and its effect on the inflammatory profile in CRC tissue ex vivo. Here, we demonstrate concentrations up 100 μM CsnB did not adversely affect tissue integrity as measured using transepithelial electrical resistance, histology and crypt height. Subsequently, we reveal through the use of a cytokine/chemokine array, ELISA and qRT-PCR analysis that multiple pro-inflammatory mediators were significantly increased in CRC tissue compared to control tissue, which were then attenuated with the addition of CsnB (such as IL-1β, IL-8 and TNFα). Lastly, stratification of the data revealed that CsnB especially alters the inflammatory profile of tumours derived from males who had not undergone chemoradiotherapy. Thus, this study demonstrates that NR4A agonist CsnB does not adversely affect colon tissue structure or functionality and can attenuate the pro-inflammatory state of human CRC tissue ex vivo.

The UCD nanosafety workshop (03 December 2018): towards developing a consensus on safe handling of nanomaterials within the Irish university labs and beyond - a report

Careful handling of the nanomaterials (NMs) in research labs is crucial to ensure a safe working environment. As the largest university in Ireland, University College Dublin (UCD) has invested significant resources to update researchers working with NMs. Due to sizes often <100 nm, the NMs including nanoparticles, harbor unprecedented materialistic properties, for example, enhanced reactivity, conductivity, fluorescence, etc. which albeit conferring the NMs an edge over bulk materials regarding the applied aspects; depending on the dose, also render them to be toxic. Thus, a set of regulatory guidelines have emerged regarding safe handling of the NMs within occupational set-ups. Unfortunately, the current regulations based on the toxic chemicals and carcinogens are often confusing, lack clarity, and difficult to apply for the NMs. As a research-intensive university, a diverse range of research activities occur within the UCD labs, and it is difficult, at times impossible, for the UCD Safety, Insurance, Operational Risk & Compliance (SIRC) office to develop a set of common guidelines and cater throughout all its labs conducting research with the NMs. Hence, a necessity for dialog and exchange of ideas was felt across the UCD which encouraged the researchers including early stage researchers (e.g. PhDs, Postdocs) from multiple schools to participate in a workshop held on the 03 December 2018. The workshop tried to follow a pragmatic approach, where apart from discussing both the in vitro and in vivo scenarios, practical cases simulating situations faced frequently in the labs were discussed. This report summarizes the findings made during the workshop by this emerging critical mass in UCD.

Protein kinase D, ubiquitin and proteasome pathways are involved in adenosine receptor-stimulated NR4A expression in myeloid cells

Adenosine is a purine nucleoside pivotal for homeostasis in cells and tissues. Stimulation of the adenosine receptors (AR) has been shown to regulate the nuclear orphan receptor 4A (NR4A1-3) family, resulting in attenuation of hyper-inflammatory responses in myeloid cells. The NR4A1-3 orphan receptors are early immediate response genes and transcriptional regulators of cell and tissue homeostasis. The signal transduction and transcriptional mechanism(s) of how AR-stimulation promotes NR4A expression in myeloid cells is unknown and is the focus of this study. We confirm that adenosine and the stable analogue, 5'-N-Ethylcarboxamidoadenosine (NECA), enhance NR4A1-3 expression in THP-1 cells. Pharmacological approaches identified that protein kinase D (PKD) mediates AR-stimulated NR4A expression in myeloid cells and reveals no involvement of PKA nor PKC. The role of NF-κB, a principal regulator of NR4A expression in myeloid cells, was examined as a possible transcriptional regulator downstream of PKD. Utilising BAY11-7082 and MG-132, inhibitors of the respective ubiquitin and proteasome pathways essential for NF-κB activation, suggested a prospective role for NF-κB, or more specifically signalling via IKKα/β. However, biological interventional studies using overexpression of IκBα in myeloid cells and MEF cells lacking IKKα and IKKβ (IKKα/β^-/-) revealed the NF-κB pathway is not utilised in mediating AR-stimulated NR4A expression. Thus, this study contributes mechanistic insight into how AR signalling modulates the expression of NR4A receptors, pivotal regulators of inflammatory responses in myeloid cells.