Regulation of lipopolysaccharide-induced inflammatory response and endotoxemia by beta-arrestins.

Department of Physiology and Division of Pathology, Michigan State University, East Lansing, Michigan 48824, USA.
Journal of Cellular Physiology (Impact Factor: 4.22). 11/2010; 225(2):406-16. DOI:10.1002/jcp.22289
Source: PubMed

ABSTRACT Beta-arrestins are scaffolding proteins implicated as negative regulators of TLR4 signaling in macrophages and fibroblasts. Unexpectedly, we found that beta-arrestin-1 (beta-arr-1) and -2 knockout (KO) mice are protected from TLR4-mediated endotoxic shock and lethality. To identify the potential mechanisms involved, we examined the plasma levels of inflammatory cytokines/chemokines in the wild-type (WT) and beta-arr-1 and -2 KO mice after lipopolysaccharide (LPS, a TLR4 ligand) injection. Consistent with lethality, LPS-induced inflammatory cytokine levels in the plasma were markedly decreased in both beta-arr-1 and -2 KO, compared to WT mice. To further explore the cellular mechanisms, we obtained splenocytes (separated into CD11(b+) and CD11(b-) populations) from WT, beta-arr-1, and -2 KO mice and examined the effect of LPS on cytokine production. Similar to the in vivo observations, LPS-induced inflammatory cytokines were significantly blocked in both splenocyte populations from the beta-arr-2 KO compared to the WT mice. This effect in the beta-arr-1 KO mice, however, was restricted to the CD11(b-) splenocytes. Our studies further indicate that regulation of cytokine production by beta-arrestins is likely independent of MAPK and IkappaBalpha-NFkappaB pathways. Our results, however, suggest that LPS-induced chromatin modification is dependent on beta-arrestin levels and may be the underlying mechanistic basis for regulation of cytokine levels by beta-arrestins in vivo. Taken together, these results indicate that beta-arr-1 and -2 mediate LPS-induced cytokine secretion in a cell-type specific manner and that both beta-arrestins have overlapping but non-redundant roles in regulating inflammatory cytokine production and endotoxic shock in mice.

0 0
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: β-arrestin 2 (β-arr2) is a scaffolding protein of the arrestin family with a wide variety of cellular functions. Recent studies have demonstrated differential roles for β-arr2 in inflammation following endotoxemia and Cecal Ligation and Puncture (CLP) models of sepsis. Because CLP-induced inflammation involves response to fecal contents and necrotic cecum in addition to microbial challenge, in this study we examined the role of β-arr2 in an exclusively polymicrobial infection (PMI) model. In addition, we examined the role of gene dosage of β-arr2 in polymicrobial sepsis. Our studies demonstrate that β-arr2 is a negative regulator of systemic inflammation in response to polymicrobial infection and that one allele is sufficient for this process. Our results further reveal that loss of β-arr2 leads to increased neutrophil sequestration and overt inflammation specifically in the lungs following polymicrobial infection. Consistent with this, specific NFκB and MAPK signaling pathways were differentially activated in the β-arr2 knockout (KO) mice lungs compared to WT following PMI. Associated with enhanced inflammation in the KO mice, PMI-induced mortality was also significantly higher in KO compared to WT mice. To understand the differential role of β-arr2 in different sepsis models, we used cell culture systems to evaluate inflammatory cytokine production following endotoxin and polymicrobial stimulation. Our results demonstrate cell type as well as stimuli-specific roles for β-arr2 in inflammation. Taken together, our results reveal a negative regulatory role for β-arr2 in polymicrobial infection-induced inflammation and further demonstrate that one allele of β-arr2 is sufficient to mediate most of these effects.
    Infection and immunity 06/2013; · 4.21 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: BACKGROUND: Esculentoside A (EsA) is a saponin isolated from the Chinese herb Phytolacca esculenta. In our study, we sought to investigate the protective effects of EsA on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. MATERIALS AND METHODS: To determine the effects of EsA on the reduction of histopathologic changes in mice with ALI, inflammatory cell count in bronchoalveolar lavage fluid (BALF) and lung wet-to-dry weight ratio were measured in LPS-challenged mice, and lung histopathologic changes observed via paraffin section were assessed. Next, cytokine production induced by LPS in BALF was measured by enzyme-linked immunosorbent assay. To further study the mechanism of EsA protective effects on ALI, IκBa, p38, and extracellular signal receptor-activated kinase pathways were investigated in lung tissue of mice with ALI. RESULTS: In the present investigation, EsA showed marked effects by reducing inflammatory infiltration, thickening of the alveolar wall, and pulmonary congestion. Levels of tumor necrosis factor α and interleukin 6 elevated by LPS were significantly decreased in BALF in EsA-pretreated ALI model. Furthermore, EsA significantly suppressed phosphorylation of IκBa, p38, and extracellular signal receptor-activated kinase. CONCLUSIONS: Taken together, our results suggest that EsA suppressed inflammatory responses in LPS-induced ALI through inhibition of the nuclear factor kappa B and mitogen activated protein kinase signaling pathways. EsA may be a promising potential preventive agent for ALI treatment.
    Journal of Surgical Research 05/2013; · 2.02 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Lithium (Li) is one of the currently prescribed drugs for bipolar disorders and has many neuro-regulatory and immune-modulating properties. Because many neuro-pathological diseases including bipolar disorders have been associated with some level of inflammation, Li's effect on inflammation may have some crucial consequences. Even though Li has been shown to have pro- and anti-inflammatory activities in different cell models, mechanisms involved in these effects are not well understood. Moreover, Li's effect on inflammation in the presence of activators of Toll-like receptors (TLRs), especially TLR-2 (that activates MyD88-dependent pathway) and TLR-3 (that activates TRIF-dependent pathway) is not known. Here we tested the role of Li in the presence and absence of TLR2, and TLR3 on MAPK and NFκB pathways and the consequent production of tumor necrosis factor-α (TNFα) in Raw264.7 macrophages. Our results indicate that Li enhances TNFα production both in the absence and presence of TLR stimulation. Interestingly, Li differentially modulates MAPK and NFκB pathways in the absence and presence of TLR2/3 ligands. Our results further indicate that the effect of Li on TNFα occurs at the post-transcriptional level. Together, these studies demonstrate that Li induces TNFα production in macrophages and that it modulates signaling at different levels depending on the presence or absence of TLR2/3 stimulation. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.
    Journal of Cellular Biochemistry 07/2013; · 3.06 Impact Factor

Full-text (2 Sources)

Available from
Nov 20, 2013