Maternal administration of probiotics promotes brain development and protects offspring's brain from postnatal inflammatory insults in C57/BL6J mice.

Neonatal morbidities are associated with long term neurological deficits in life and have also been associated with dysbiosis. We tested whether optimizing the neonate's microbiome through maternal probiotic supplementation can improve offspring's neurodevelopmental outcomes. Maternal LB supplementation, carried out by giving Lactobacillus acidophilus and Bifidobacterium infantis (LB) to pregnant C57/BL6J mice daily from E16 to weaning, significantly suppressed postnatal peripheral proinflammatory insult-induced systemic inflammation and normalized compromised blood-brain barrier permeability and tight junction protein expression in the offspring at pre-weaned age. Maternal LB exposure also regulated markers associated with leukocyte transendothelial migration, extracellular matrix injury and neuroinflammation. The suppressed neuroinflammation by maternal LB supplementation was associated with reduced astrocyte/microglia activation and downregulation of the transcriptional regulators CEBPD and IκBα. Furthermore, maternal LB supplementation promoted neuronal and oligodendrocyte progenitor cell development. Our study demonstrates the efficacy of maternal LB supplementation in modulating systemic and central nervous system inflammation as well as promoting neural/oligodendrocyte progenitor development in the offspring. This evidence suggests that maternal probiotic supplementation may be a safe and effective strategy to improve neurological outcomes in the offspring.

CCAAT/enhancer binding protein δ in macrophages contributes to immunosuppression and inhibits phagocytosis in nasopharyngeal carcinoma.

Although tumors tend to be associated with immune cells and inflammation, this immune response often fails to eliminate the cancer and instead promotes cancer progression. Tumor-associated macrophages (TAMs) fail to phagocytose tumor cells, and they also produce signals that suppress the adaptive immune response. We showed that immunosuppressive prostaglandin E2 (PGE2) led to the production and activity of the transcription factor CCAAT/enhancer binding protein δ (C/EBPδ) by stimulating the nucleocytoplasmic shuttling of the RNA binding protein Hu antigen R (HuR), which bound to and stabilized CEBPD mRNA in macrophages. An increase in C/EBPδ abundance in macrophages in response to PGE2 resulted in enhanced production of the immunosuppressive cytokine interleukin-10 (IL-10) and of pentraxin 3 (PTX3), which suppresses the ability of macrophages to phagocytose tumor cells. Furthermore, conditioned medium from C/EBPδ-replete, but not C/EBPδ-deficient, macrophages inhibited the phagocytosis of tumor cells by macrophages, suggesting an autocrine mode of regulation. Immunohistochemical analysis demonstrated that the amount of cytosolic HuR protein correlated with increased C/EBPδ abundance in TAMs in malignant nasopharyngeal carcinoma. Together, these data suggest that the inflammatory PGE2-HuR-C/EBPδ axis in macrophages promotes tumor progression by preventing the phagocytosis of tumor cells and inducing immunosuppressive cytokine production.

Myeloid depletion of SOCS3 enhances LPS-induced acute lung injury through CCAAT/enhancer binding protein δ pathway.

Although uncontrolled inflammatory response plays a central role in the pathogenesis of acute lung injury (ALI), the precise molecular mechanisms underlying the development of this disorder remain poorly understood. SOCS3 is an important negative regulator of IL-6-type cytokine signaling. SOCS3 is induced in lung during LPS-induced lung injury, suggesting that generation of SOCS3 may represent a regulatory product during ALI. In the current study, we created mice lacking SOCS3 expression in macrophages and neutrophils (LysM-cre SOCS3(fl/fl)). We evaluated the lung inflammatory response to LPS in both LysM-cre SOCS3(fl/fl) mice and the wild-type (WT) mice (SOCS3(fl/fl)). LysM-cre SOCS3(fl/fl) mice displayed significant increase of the lung permeability index (lung vascular leak of albumin), neutrophils, lung neutrophil accumulation (myeloperoxidase activity), and proinflammatory cytokines/chemokines in bronchial alveolar lavage fluids compared to WT mice. These phenotypes were consistent with morphological evaluation of lung, which showed enhanced inflammatory cell influx and intra-alveolar hemorrhage. We further identify the transcription factor, CCAAT/enhancer-binding protein (C/EBP) δ as a critical downstream target of SOCS3 in LPS-induced ALI. These results indicate that SOCS3 has a protective role in LPS-induced ALI by suppressing C/EBPδ activity in the lung. Elucidating the function of SOCS3 would represent prospective targets for a new generation of drugs needed to treat ALI.

CCAAT/enhancer-binding protein δ facilitates bacterial dissemination during pneumococcal pneumonia in a platelet-activating factor receptor-dependent manner.

CCAAT/enhancer-binding protein δ (C/EBPδ) recently emerged as an essential player in the inflammatory response to bacterial infections. C/EBPδ levels increase rapidly after a proinflammatory stimulus, and increasing C/EBPδ levels seem to be indispensable for amplification of the inflammatory response. Here we aimed to elucidate the role of C/EBPδ in host defense in community-acquired pneumococcal pneumonia. We show that C/EBPδ(-/-) mice are relatively resistant to pneumococcal pneumonia, as indicated by delayed and reduced mortality, diminished outgrowth of pneumococci in lungs, and reduced dissemination of the infection. Moreover, expression of platelet-activating factor receptor (PAFR), which is known to potentiate bacterial translocation of gram-positive bacteria, was significantly reduced during infection in C/EBPδ(-/-) mice compared with WT controls. Importantly, cell stimulation experiments revealed that C/EBPδ potentiates PAFR expression induced by lipoteichoic acid and pneumococci. Thus, C/EBPδ exaggerates bacterial dissemination during Streptococcus pneumoniae-induced pulmonary infection, suggesting an important role for PAFR-dependent bacterial translocation.

C/EBP{delta} and STAT-1 are required for TLR8 transcriptional activity.

Toll-like receptor 8 (TLR8), which is expressed primarily in myeloid cells, plays a central role in initiating immune responses to viral single-stranded RNA. Despite the great interest in the field of TLR8 research, very little is known in terms of TLR8 biology and its transcriptional regulation. Here, we describe the isolation of the hTLR8 promoter and the characterization of the molecular mechanisms involved in its regulation. Reporter gene analysis and ChIP assays demonstrated that the hTLR8 regulation of the basal transcription is regulated via three C/EBP cis-acting elements that required C/EBPδ and C/EBPß activity. In addition, we observed that R848 stimulation increases TLR8 transcriptional activity via an enhanced binding of C/EBPδ, and not C/EBPß, to its responsive sites within the TLR8 promoter. Moreover, we showed that IFN-γ also increased TLR8 transcription activity via the binding of STAT1 transcription factor to IFN-γ activated sequence elements on the TLR8 promoter and enhanced TLR8 functionality. These results shed new light on the mechanisms involved during TLR8-mediated innate immune response.

Function of C/EBPdelta in a regulatory circuit that discriminates between transient and persistent TLR4-induced signals.

The innate immune system is like a double-edged sword: it is absolutely required for host defense against infection, but when uncontrolled, it can trigger a plethora of inflammatory diseases. Here we use systems-biology approaches to predict and confirm the existence of a gene-regulatory network involving dynamic interaction among the transcription factors NF-kappaB, C/EBPdelta and ATF3 that controls inflammatory responses. We mathematically modeled transcriptional regulation of the genes encoding interleukin 6 and C/EBPdelta and experimentally confirmed the prediction that the combination of an initiator (NF-kappaB), an amplifier (C/EBPdelta) and an attenuator (ATF3) forms a regulatory circuit that discriminates between transient and persistent Toll-like receptor 4-induced signals. Our results suggest a mechanism that enables the innate immune system to detect the duration of infection and to respond appropriately.

CCAAT/enhancer-binding protein beta and delta binding to CIITA promoters is associated with the inhibition of CIITA expression in response to Mycobacterium tuberculosis 19-kDa lipoprotein.

TLR2 signaling by Mycobacterium tuberculosis 19-kDa lipoprotein (LpqH) inhibits IFN-gamma-induced expression of CIITA by macrophages. Microarray analysis, quantitative RT-PCR, and Western blots showed that LpqH induced C/EBPbeta and C/EBPdelta in kinetic correlation with inhibition of CIITA expression. Of the C/EBPbeta isoforms, liver inhibitory protein (LIP) was notably induced and liver-activating protein was increased by LpqH. Putative C/EBP binding sites were identified in CIITA promoters I and IV (pI and pIV). LpqH induced binding of C/EBPbeta (LIP and liver-activating protein) to biotinylated oligodeoxynucleotide containing the pI or pIV binding sites, and chromatin immunoprecipitation showed that LpqH induced binding of C/EBPbeta and C/EBPdelta to endogenous CIITA pI and pIV. Constitutive expression of C/EBPbeta LIP inhibited IFN-gamma-induced CIITA expression in transfected cells. In summary, LpqH induced expression of C/EBPbeta and C/EBPdelta, and their binding to CIITA pI and pIV, in correlation with inhibition of IFN-gamma-induced expression of CIITA in macrophages, suggesting a role for C/EBP as a novel regulator of CIITA expression.