Edward L. Nelson

Mutual repression between steroid and xenobiotic receptor and NF-κB signaling pathways links xenobiotic metabolism and inflammation

While it has long been known that inflammation and infection reduce expression of hepatic cytochrome P450 (CYP) genes involved in xenobiotic metabolism and that exposure to xenobiotic chemicals can impair immune function, the molecular mechanisms underlying both of these phenomena have remained largely unknown. Here we show that activation of the nuclear steroid and xenobiotic receptor (SXR) by commonly used drugs in humans inhibits the activity of NF-kappaB, a key regulator of inflammation and the immune response. NF-kappaB target genes are upregulated and small bowel inflammation is significantly increased in mice lacking the SXR ortholog pregnane X receptor (PXR), thereby demonstrating a direct link between SXR and drug-mediated antagonism of NF-kappaB. Interestingly, NF-kappaB activation reciprocally inhibits SXR and its target genes whereas inhibition of NF-kappaB enhances SXR activity. This SXR/PXR-NF-kappaB axis provides a molecular explanation for the suppression of hepatic CYP mRNAs by inflammatory stimuli as well as the immunosuppressant effects of xenobiotics and SXR-responsive drugs. This mechanistic relationship has clinical consequences for individuals undergoing therapeutic exposure to the wide variety of drugs that are also SXR agonists.

Prenatal psychosocial stress exposure is associated with insulin resistance in young adults

OBJECTIVE The objective of the study was to examine the association in humans between maternal psychosocial stress exposure during pregnancy and measures of glucose-insulin metabolism in the adult offspring. STUDY DESIGN Healthy young adults whose mothers experienced major stressful life events during their pregnancy (n = 36, prenatal stress, PS group, mean age 25 +/- 5.14 [SD] years) and a comparison group (n = 22, CG, mean age 24 +/- 3.7 [SD] years) underwent an oral glucose tolerance test. RESULTS Glucose levels were not significantly different across the groups; however, prenatally stressed subjects showed significantly elevated 2-hour insulin (P = .01) and C-peptide levels (P = .03). These differences were independent of other major risk factors for insulin resistance, including birth phenotype (birthweight, length of gestation), a family history of diabetes, gestational diabetes, body mass index, proinflammatory state, and smoking. CONCLUSION Higher insulin responses reflect relative insulin resistance in these prenatally stressed young adults. This study is the first to provide evidence for a link in humans between prenatal psychosocial stress exposure and alterations in glucose-insulin metabolic function.

Longitudinal modulation of immune system cytokine profile during pregnancy.

OBJECTIVE To characterize immune modulation as expressed by cytokine assays at three time-points in human pregnancy. STUDY DESIGN This is a prospective, longitudinal study of a broad panel of cytokine expression during singleton pregnancies resulting in an uncomplicated, full-term, live births. Peripheral blood was obtained at 8-14, 18-22, and 28-32 weeks gestation. Six cytokines - IFN-γ, IL-4, TNF-α, IL-1β, IL-6, and IL-10 - were measured in supernatants obtained from whole blood stimulations with PHA or LPS and were compared to unstimulated controls. Samples were processed by Luminex-100 MAP®. We used Generalized Linear Models (GLM) to evaluate cytokine trajectories. RESULTS Complete data were obtained for 45 uncomplicated pregnancies. Overall, peripheral blood WBCs demonstrated dampened cytokine responses. However, over the course of pregnancy, we found enhanced counter-regulatory cytokine expression (e.g., shown by increased IL-10). CONCLUSION The overall decrease in pro-inflammatory cytokines and increase in counter-regulatory cytokines as uncomplicated pregnancy progresses supports the evolving concepts of immunoregulation for the maintenance of a viable pregnancy.

C1q Differentially Modulates Phagocytosis and Cytokine Responses during Ingestion of Apoptotic Cells by Human Monocytes, Macrophages, and Dendritic Cells

C1q, the first component of the classical complement pathway, is also a pattern recognition receptor involved in the recognition and clearance of apoptotic cells. C1q deficiency in humans leads to development of lupus-like autoimmune disease, and it has been speculated that impaired clearance of apoptotic cells may contribute to disease development. Since phagocytes initiate specific and appropriate immune responses as a result of initial ligand-receptor interactions, regulation of gene expression by C1q may also contribute to the sculpting of an immune response to the ingested “self-Ags.” In this study, the role of C1q in apoptotic cell clearance and subsequent modulation of cytokine release by phagocytes was assessed including donor matched human monocytes, monocyte-derived macrophages (HMDMs), and dendritic cells (DCs). First, C1q binding is much greater to late compared with early apoptotic cells. Second, C1q binding to apoptotic cells significantly enhanced the levels of ingestion by monocytes but had no effect on HMDM and DC uptake. Third, in the presence of serum, C1q bound to apoptotic cells, activated the complement pathway, leading to C3b deposition, and enhancement of uptake of apoptotic cells by monocytes, HMDMs, and DCs. Finally, although C1q, either immobilized on a plate or bound to apoptotic cells, modulates the LPS-induced cytokine levels released by human monocytes, HMDMs, and DCs toward a more limited immune response, both the degree and direction of modulation differed significantly depending on the differentiation state of the phagocyte, providing further evidence of the integration of these cell- and environment-specific signals in determining appropriate immune responses.

Influence of prenatal psychosocial stress on cytokine production in adult women.

The aim of the present study was to determine the association between prenatal stress and immune function in human adults. Peripheral blood mononuclear cells (PBMCs) from 34 healthy young women whose mothers experienced major negative life events during their pregnancy (Prenatal Stress, PS group, mean age 25, SD +/- 4.34 years), and from a female comparison group (n = 28, CG, mean age 24 +/- 3.40 years), were stimulated with phytohemagglutinin (PHA), and subsequent cytokine production was measured. A bias for T-helper 2 (Th2) cytokine production due to an overproduction of IL-4 relative to IFN-gamma after PHA stimulation was observed in PS subjects. In addition, IL-6 and IL-10 were also significantly elevated. To the best of our knowledge, this study is the first to suggest a direct association between prenatal stress exposure and alterations in immune parameters in adult women.

ATF and Jun transcription factors, acting through an Ets / CRE promoter module, mediate lipopolysaccharide inducibility of the chemokine RANTES in monocytic Mono Mac 6 cells

The chemokine RANTES is produced by a variety of tissues, including cells of the monocyte / macrophage lineage. RANTES expression is rapidly and transiently up‐regulated in primary monocytes and the monocytic cell line Mono Mac 6 in response to stimulation by the bacterial product lipopolysaccharide (LPS). Transient transfection of Mono Mac 6 cells with RANTES reporter‐promoter deletion constructs, in conjunction with DNase I footprinting and heterologous reporter gene assays, allowed identification of an LPS‐responsive region within the RANTES promoter. Electrophoretic mobility shift assays (EMSA), methylation interference and EMSA supershift experiments were used to characterize sequences and transcription factors responsible for this LPS inducibility. The region, termed RANTES site G [R(G)], contains consensus sites for Ets and CRE / AP‐1‐like elements. Site‐directed mutagenesis of the Ets site resulted in a loss of only 15 % of promoter activity, while mutation of the CRE / AP‐1 site led to a loss of 40 % of LPS‐induced promoter activity. The Ets site constitutively binds the Ets family member PU.1. LPS stimulation leads to an induction of ATF‐3 and JunD factor binding to the CRE / AP‐1 site. Thus, LPS induction of RANTES transcription is mediated, in part, through the activation and selective binding of ATF and Jun nuclear factors to the R(G) promoter module.

Three-color flow cytometric assay for the study of the mechanisms of cell-mediated cytotoxicity

Cytotoxic lymphocytes kill tumor or virus-infected target cells utilizing two mechanisms (1) release of lytic granules (containing perforin and granzymes) and (2) Fas ligand (FasL)/Fas or TNF initiated apoptosis. We have examined mechanisms of target cell lysis using a new Flow Cytometric Cytotoxicity Assay (FC Assay). Target cells were labeled with PKH 67 dye. Cell death was estimated by 7-amino-actinomycin (7-AAD) inclusion and annexin V-PE binding. A strong direct correlation has been found between the percentage of dead target cells in the FC Assay and the results of 51Cr release assay when human LAK and CTL were used as a model system. We have shown that both NK and CTL kill tumor cells mostly by granule-mediated mechanisms, as lysis was blocked by a perforin inhibitor Concanamycin A (Folimycin) but was significantly less sensitive to zVAD-FMK caspase inhibition. The FC assay allows accurate measurement of cell-mediated cytotoxicity as individual target cell death is detected directly.

Molecular and in silico characterization of a promoter module and C/EBP element that mediate LPS-induced RANTES/CCL5 expression in monocytic cells

The chemokine RANTES/CCL5 is a proinflammatory agent produced by a variety of tissues in response to specific stimuli. In human monocytes, RANTES/CCL5 transcription is up‐regulated rapidly and transiently in response to LPS. We describe here two regions that help control LPS‐driven transcription from the human RANTES/CCL5 promoter in monocytic cells. These sites were analyzed by using DNase I footprinting, transient transfection assays, site‐directed mutagenesis, and EMSA. RANTES site E (R(E), ‐125/‐99) constitutively binds C/EBP proteins in monocytic Mono Mac 6 cells. Mutation of region R(E) led to a significant (40%–50%) reduction in LPS‐induced promoter reporter activity. Region R(AB) is composed of tandem κB‐like elements R(A) and R(B) (‐73/‐34). These sites working in concert act as an LPS‐responsive promoter module. R(A) constitutively binds Sp1, and Rel p50/p65 following LPS stimulation. Either factor can mediate transcriptional effects at R(A). Induced Rel p50/p50 binding to site R(B) is required for LPS regulation of RANTES/CCL5 transcription. A series of computer models based on the RANTES/CCL5 promoter were generated to represent the organization of these functional elements. The models could identify LPS‐regulated promoters in human, other vertebrate, and viral sequences in various databases.

Stress, Immunity, and Cervical Cancer: Biobehavioral Outcomes of a Randomized Clinical Trail

Purpose: Cancer diagnosis and treatment imparts chronic stressors affecting quality of life (QOL) and basic physiology. However, the capacity to increase survival by improving QOL is controversial. Patients with cervical cancer, in particular, have severely compromised QOL, providing a population well-suited for the evaluation of novel psychosocial interventions and the exploration of mechanisms by which modulation of the psychoneuroimmune axis might result in improved clinical outcomes. Experimental Design: A randomized clinical trial was conducted in cervical cancer survivors that were enrolled at ≥13 and <22 months after diagnosis (n = 50), comparing a unique psychosocial telephone counseling (PTC) intervention to usual care. QOL and biological specimens (saliva and blood) were collected at baseline and 4 months post-enrollment. Results: The PTC intervention yielded significantly improved QOL (P = 0.011). Changes in QOL were significantly associated with a shift of immune system T helper type 1 and 2 (Th1/Th2) bias, as measured by IFN-γ/interleukin-5 ELISpot T lymphocyte precursor frequency; improved QOL being associated with increased Th1 bias (P = 0.012). Serum interleukin-10 and the neuroendocrine variables of cortisol and dehydroepiandrosterone revealed trends supporting this shift in immunologic stance and suggested a PTC-mediated decrease of the subjects chronic stress response. Conclusions: This study documents the utility of a unique PTC intervention and an association between changes in QOL and adaptive immunity (T helper class). These data support the integration of the chronic stress response into biobehavioral models of cancer survivorship and suggests a novel mechanistic hypotheses by which interventions leading to enhanced QOL could result in improved clinical outcome including survival.

Fibrinogen Induces IL-8 Synthesis in Human Neutrophils Stimulated with Formyl-Methionyl-Leucyl-Phenylalanine or Leukotriene B 4

Human exudative neutrophils have greatly increased stores of the neutrophil chemoattractant IL-8 compared with peripheral blood cells, but the mechanism for the increase is not defined. In this report, we show that treatment of peripheral blood neutrophils with the chemotactic peptide fMLP or with leukotriene B4 or fibrinogen results in little increase in the production of IL-8 by peripheral blood neutrophils. However, a chemotactically active dose of fMLP (5 × 10−9 M) or leukotriene B4 (1 × 10−7 M) in the presence of a physiological concentration (2 mg/ml) of fibrinogen results in a receptor-mediated, pertussis toxin-sensitive, synergistic 30-fold increase in IL-8 synthesis. The levels of IL-8 attained are comparable to those observed in exudative cells. Higher concentrations of fMLP (1 × 10−7 M) are associated with reduced IL-8 protein synthesis without IL-8 degradation, indicating a sensitive regulatory mechanism for IL-8 production. Treatment of neutrophils with fibrinogen and fMLP resulted in minimal changes in the steady state levels of mRNA for macrophage inflammatory protein-1α and -1β and monocyte chemoattractant protein-1. In contrast, in the presence of fibrinogen, the steady-state level of neutrophil IL-8 mRNA increased 8-fold with 5 × 10−9 M fMLP but was not decreased with 1 × 10−7 M fMLP, suggesting that neutrophils are specifically adapted to modulate neutrophil IL-8 synthesis through transcriptional and posttranscriptional mechanisms. The data indicate that fibrinogen can function not only as a substrate in the clotting cascade, but also as an important effector during the evolution of the innate immune response.