Differential induction of JE/MCP-1 in subclones from a murine macrophage cell line, RAW 264.7: role of kappaB-3 binding protein

Low-intensity pulsed ultrasound (LIPUS) inhibits LPS-induced inflammatory responses of osteoblasts through TLR4-MyD88 dissociation

Previous reports have shown that osteoblasts are mechano-sensitive. Low-intensity pulsed ultrasound (LIPUS) induces osteoblast differentiation and is an established therapy for bone fracture. Here we have examined how LIPUS affects inflammatory responses of osteoblasts to LPS. LPS rapidly induced mRNA expression of several chemokines including CCL2, CXCL1, and CXCL10 in both mouse osteoblast cell line and calvaria-derived osteoblasts. Simultaneous treatment by LIPUS significantly inhibited mRNA induction of CXCL1 and CXCL10 by LPS. LPS-induced phosphorylation of ERKs, p38 kinases, MEK1/2, MKK3/6, IKKs, TBK1, and Akt was decreased in LIPUS-treated osteoblasts. Furthermore, LIPUS inhibited the transcriptional activation of NF-κB responsive element and Interferon-sensitive response element (ISRE) by LPS. In a transient transfection experiment, LIPUS significantly inhibited TLR4-MyD88 complex formation. Thus LIPUS exerts anti-inflammatory effects on LPS-stimulated osteoblasts by inhibiting TLR4 signal transduction.

LPS-induced chemokine expression in both MyD88-dependent and -independent manners is regulated by Cot/Tpl2-ERK axis in macrophages

LPS signaling is mediated through MyD88-dependent and -independent pathways, activating NF-?B, MAP kinases and IRF3. Cot/Tpl2 is an essential upstream kinase in LPS-mediated activation of ERKs. Here we explore the roles of MyD88 and Cot/Tpl2 in LPS-induced chemokine expression by studying myd88(-/-) and cot/tpl2(-/-) macrophages. Among the nine LPS-responsive chemokines examined, mRNA induction of ccl5, cxcl10, and cxcl13 is mediated through the MyD88-independent pathway. Notably, Cot/Tpl2-ERK signaling axis exerts negative effects on the expression of these three chemokines. In contrast, LPS-induced gene expression of ccl2, ccl7, cxcl2, cxcl3, ccl8, and cxcl9 is mediated in the MyD88-dependent manner. The Cot/Tpl2-ERK axis promotes the expression of the first four and inhibits the expression of the latter two. Thus, LPS induces expression of multiple chemokines through various signaling pathways in macrophages.

Glycyrrhiza inflata-derived chalcones, Licochalcone A, Licochalcone B and Licochalcone D, inhibit phosphorylation of NF-kappaB p65 in LPS signaling pathway

Licorice root has been used as a traditional medicine for the treatment of gastric ulcer, bronchial asthma and inflammation. Licochalcone A is a major component of Xinjiang licorice, Glycyrrhiza inflata. Previously we showed that Licochalcone A significantly inhibited LPS-induced NF-kappaB transcriptional activation by abrogating the phosphorylation of NF-kappaB p65 at serine 276. Glycyrrhiza inflata contains not only Licochalcone A but also Licochalcone B, Licochalcone C, Licochalcone D, Echinatin and Isoliquiritigenin, harboring the common structure of chalcones. No chalcones had any effect on LPS-induced IkappaB degradation, nuclear translocation and DNA binding activity of NF-kappaB p65; however, we observed that Licochalcone B and Licochalcone D significantly inhibited LPS-induced phosphorylation at serine 276 and transcriptional activation of NF-kappaB, the same as Licochalcone A. Interestingly, we also found that Licochalcone A, Licochalcone B and Licochalcone D effectively inhibited LPS-induced activation of PKA, which is required for the phosphorylation of NF-kappaB p65 at serine 276. Consequently, Licochalcone B and Licochalcone D significantly reduced the LPS-induced production of NO, TNFalpha and MCP-1. On the other hand, Licochalcone C, Echinatin and Isoliquitigenin failed to inhibit LPS-induced NF-kappaB activation. These findings suggest that the anti-inflammatory effect of Glycyrrhiza inflata is ascribable to the potent inhibition of NF-kappaB by Licochalcone A, Licochalcone B and Licochalcone D.

C/EBPbeta serine 64, a phosphoacceptor site, has a critical role in LPS-induced IL-6 and MCP-1 transcription

C/EBPbeta is a member of the CCAAT/enhancer binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of various proinflammatory genes, including IL-6 and MCP-1. Serine 64 in the transactivation domain of C/EBPbeta has recently been identified as a Ras-induced phosphoacceptor site. The integrity of serine 64 along with threonine 189 is important for the Ha-ras(V12)-induced transformation of NIH3T3 cells, however no target genes dependent upon serine 64 for their expression have been reported. In order to evaluate a potential role of serine 64 in C/EBPbeta-regulated cytokine expression, we expressed a form of C/EBPbeta with an alanine substitution at serine 64 (C/EBPbeta(S64A)) in P388 murine B lymphoblasts, which lack endogenous C/EBPbeta expression and are normally unresponsive to LPS for expression of IL-6 and MCP-1. In comparison to wild type C/EBPbeta, which robustly supports the LPS-induced expression of IL-6 and MCP-1, C/EBPbeta(S64A) was severely impaired in its ability to support the LPS-induced transcription of IL-6 and MCP-1. Furthermore, LPS stimulation increased the level of phosphorylation detected at serine 64. Thus, serine 64, probably through its phosphorylation, is a critical determinant of C/EBPbeta activity in the transcription of IL-6 and MCP-1.

Characterization of the molecular clock in mouse peritoneal macrophages

Macrophages play essential roles in the innate immune system. In this study, we show that macrophage functions such as phagocytosis and cytokine/chemokine expressions display a circadian rhythm that is regulated by a molecular clock. Phagocytosis, a crucial early reaction by which macrophages protect their host against foreign particles, exhibited a circadian variation that peaks during the light period and bottoms during the dark period. These diurnal changes of phagocytosis activity in macrophages were induced without exogenous stimulants such as bacterial infection. The expression of the clock genes including brain and muscle Arnt-like protein-1 (BMAL1) exhibited robust circadian rhythms in macrophages. The expression patterns of the clock genes in macrophages were similar to those in the suprachiasmatic nucleus and other peripheral tissues. Among inflammation factors examined, the level of monocyte chemoattractant protein-1 (MCP-1/JE) mRNA exhibited most robust circadian oscillation. Expression of other cytokines such as IL-1beta, IL-6 and TNFalpha showed mild diurnal changes. Knockdown of the BMAL1 expression resulted in a decrease of the MCP-1/JE mRNA level in macrophages. BMAL1 increased significantly but weakly MCP-1/JE promoter activity. MCP-1/JE promoter activity is known to be regulated by nuclear factor-kappa B (NF-kappaB). NF-kappaB activity in BMAL1 knockdown macrophages was lower than that in control cells. Consequently, the circadian expression of MCP-1/JE in macrophages is regulated by BMAL1 through the activation of NF-kappaB. The results obtained in this study indicate that the innate immunoreactions involving macrophages are at least partly regulated by the autonomous clock machinery.

Differential roles of C/EBP beta regulatory domains in specifying MCP-1 and IL-6 transcription

C/EBPbeta is a member of the CCAAT/enhancer binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of various proinflammatory genes, including IL-6 and MCP-1. To examine the roles of the C/EBPbeta transactivation and regulatory domains in LPS-induced MCP-1 and IL-6 expression, we expressed various N-terminal truncations and deletions of C/EBPbeta in P388 murine B lymphoblasts, which lack endogenous C/EBPbeta expression and are normally unresponsive to LPS for expression of IL-6 and MCP-1. Unexpectedly, a region between amino acids 105 and 212 of C/EBPbeta that includes regulatory domains 1 and 2 facilitates C/EBPbeta activation of IL-6 expression, while having an inhibitory effect on MCP-1 expression. Thus, this region can mediate promoter-specific effects on cytokine and chemokine gene transcription. LIP, the naturally occurring truncated form of C/EBPbeta, largely retains these regulatory domains and stimulates IL-6 but not MCP-1 transcription.

Endotoxin recognition: in fish or not in fish?

The interaction between pathogens and their multicellular hosts is initiated by activation of pathogen recognition receptors (PRRs). These receptors, that include most notably members of the toll-like receptor (TLR) family, recognize specific pathogen-associated molecular patterns (PAMPs). TLR4 is a central part of the receptor complex that is involved in the activation of the immune system by lipopolysaccharide (LPS) through the specific recognition of its endotoxic moiety (Lipid A). This is a critical event that is essential for the immune response to Gram-negative bacteria as well as the etiology of endotoxic shock. Interestingly, compared to mammals, fish are resistant to endotoxic shock. This in vivo resistance concurs with in vitro studies demonstrating significantly lowered sensitivity of fish leukocytes to LPS activation. Further, our in vitro analyses demonstrate that in trout mononuclear phagocytes, LPS fails to induce antiviral genes, an event that occurs downstream of TLR4 and is required for the development of endotoxic shock. Finally, an in silico approach that includes mining of different piscine genomic and EST databases, reveals the presence in fish of all of the major TLR signaling elements except for the molecules specifically involved in TLR4-mediated endotoxin recognition and signaling in mammals. Collectively, our analysis questions the existence of TLR4-mediated cellular responses to LPS in fish. We further speculate that other receptors, in particular beta-2 integrins, may play a primary role in the activation of piscine leukocytes by LPS.

Identification of expressed genes in regenerating rat liver in 0-4-8-12 h short interval successive partial hepatectomy

AIM: To identify the genes differentially expressed in the regenerating rat liver of 0-4-8-12 h short interval successive partial hepatectomy (SISPH) and to analyze their expression profiles.

METHODS: Five hundred and fifty-one elements screened from subtractive cDNA libraries were made into a cDNA microarray (cDNA chip). Extensive gene expression analysis following 0-4-8-12 h SISPH was conducted by microarray.

RESULTS: One hundred and eighty-three elements were selected, which were either up- or down-regulated more than 2-fold at one or more time points after SISPH. Cluster analysis and generalization analysis showed that there were five distinct temporal patterns of gene expression. Eighty-six genes were unreported, associated with liver regeneration (LR).

CONCLUSION: Microarray analysis shows that the down regulated genes are much more than the up-regulated ones in SISPH; the numbers of genes expressed consistently are fewer than that expressed immediately; the genes expressed in high abundance are much fewer than that increased 2-5-fold. The comparison of SISPH with partial hepatectomy (PH) shows that the expression trends of most genes in SISPH and in PH are similar, but the expression of 43 genes is specifically altered in SISPH.

Activation of rainbow trout (Oncorhynchus mykiss) mononuclear phagocytes by different pathogen associated molecular pattern (PAMP) bearing agents

Rainbow trout (Oncorhynchus mykiss) cells of a monocyte-macrophage lineage (rtMOCs) were used to characterize the ability of the trout innate immune system to recognize and respond to different pathogen associated molecular pattern (PAMP) bearing substances. Compared to what has been reported for mammalian macrophages, rtMOCs responded with lower sensitivity to lipopolysaccharide (LPS) from Escherichia coli (EC-LPS) and Pseudomonas aeruginosa (PA-LPS). The sensitivity of rtMOCs to LPS was not influenced by the presence of serum which suggests that the resistance to endotoxic shock in fish may be due to the lack of serum-borne factors that confer sensitivity to LPS in mammals. The time course of the response to PAMPs could be separated into two patterns. EC-LPS induced stable cytokine expression whereas PA-LPS, zymosan and muramyl dipeptide induced transient TNF2 expression. By analogy to the type of stimulation observed in mammals it can be hypothesized that different signaling pathways, possibly initiated by different receptors, may be involved in the recognition of these PAMPs by rtMOCs.

Activated protein C inhibits the release of macrophage inflammatory protein-1-alpha from THP-1 cells and from human monocytes

Several lines of evidence have implicated activated protein C (APC) to be an endogenous inhibitor of the inflammatory septic cascade. APC may exhibit direct anti-inflammatory properties, independent of its antithrombotic effects. Chemokines influence the interaction of monocytes at the endothelium during infection and sepsis and are involved in the molecular events leading to an adverse and lethal outcome of sepsis. Defining regulatory mechanisms on the monocytic release profile of the proinflammatory C-C chemokines macrophage inflammatory protein-1-alpha (MIP-1-alpha) and monocyte chemoattractant protein-1 (MCP-1) might have therapeutic implications for the treatment of sepsis. We established a monocytic cell model of inflammation by the addition of lipopolysaccharide (LPS) and examined the effect of human APC on LPS-stimulated chemokine release from the monocytic cell line THP-1. We found that human APC in supra-physiological concentrations of 2.5-10 microg/ml inhibited the LPS-induced release of the chemokines MIP-1-alpha and MCP-1, as measured by enzyme-linked immunosorbent assays (ELISA) at 6 up to 24 h. In addition to experiments on THP-1 cells, recombinant human APC in concentrations of 50 ng/ml was found to have an inhibiting effect on the release of MIP-1-alpha from freshly isolated mononuclear cells of septic patients. The ability of APC to decrease the release of the C-C chemokine MIP-1-alpha from the monocytic cell line THP-1 and from human monocytes may identify a novel immunomodulatory pathway by which APC exerts its anti-inflammatory action and may contribute to control the inflammatory response in sepsis.

Altered expression of immune modulator and structural genes in neonatal unilateral ureteral obstruction

BACKGROUND

Congenital obstructive nephropathy is a condition characterized by hydronephrosis, tubular dilatation, apoptosis, and atrophy, as well as interstitial cellular infiltration and progressive interstitial fibrosis. The renal consequences of chronic unilateral ureteral obstruction (UUO) in the neonatal rat are similar to those of clinical congenital obstructive nephropathy.

METHODS

To define alterations in renal gene expression induced by chronic neonatal UUO, Sprague-Dawley rats were subjected to UUO or sham operation within the first 2 days of life, and kidneys were harvested after 12 days.

RESULTS

Microarray analysis revealed that the mRNA expression of multiple immune modulators, including krox24, interferon-gamma regulating factor-1 (IRF-1), monocyte chemoattractant protein-1 (MCP-1), interleukin-1beta (IL-1beta), CCAAT/enhancer binding protein (C/EBP), p21, c-fos, c-jun, and pJunB, was significantly increased in obstructed compared to sham-operated kidneys (all P < 0.05). Western blot analysis revealed significant changes in immune modulator protein abundance in the obstructed versus sham-operated kidney for krox24 (P = 0.0004), IRF-1 (P = 0.005), MCP-1 (P = 0.01), and JunD (P = 0.0008). Alternatively, the abundance of all of the immune modulator proteins was similar in sham-operated and obstructed kidneys in rats subjected to acute (4 days) neonatal UUO. Microarray analysis studies also reveal that structural genes that comprise the cytoskeleton and cell matrix are significantly up-regulated by chronic neonatal UUO, including calponin, desmin, dynamin, and lumican (all P < 0.05).

CONCLUSION

Multiple genes are aberrantly expressed in the kidney of rats subjected to chronic neonatal UUO. Elucidation of these genes involved in neonatal UUO may lead to new insight about congenital obstructive nephropathy.

Roles of toll-like receptors in C-C chemokine production by renal tubular epithelial cells

Pyelonephritis, in which renal tubular epithelial cells are directly exposed to bacterial component, is a major predisposing cause of renal insufficiency. Although previous studies have suggested C-C chemokines are involved in the pathogenesis, the exact source and mechanisms of the chemokine secretion remain ambiguous. In this study, we evaluated the involvement of Toll-like receptors (TLRs) in C-C chemokine production by mouse primary renal tubular epithelial cells (MTECs). MTECs constitutively expressed mRNA for TLR1, 2, 3, 4, and 6, but not for TLR5 or 9. MTECs also expressed MD-2, CD14, myeloid differentiation factor 88, and Toll receptor-IL-1R domain-containing adapter protein/myeloid differentiation factor 88-adapter-like. Synthetic lipid A and lipoprotein induced monocyte chemoattractant protein 1 (MCP-1) and RANTES production in MTECs, which strictly depend on TLR4 and TLR2, respectively. In contrast, MTECs were refractory to CpG-oligodeoxynucleotide in chemokine production, consistently with the absence of TLR9. LPS-mediated MCP-1 and RANTES production in MTECs was abolished by NF-kappaB inhibition, but unaffected by extracellular signal-regulated kinase inhibition. In LPS-stimulated MTECs, inhibition of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase significantly decreased RANTES, but did not affect MCP-1 mRNA induction. Thus, MTECs have a distinct expression pattern of TLR and secrete C-C chemokines in response to direct stimulation with a set of bacterial components.