Does maternal feeding restriction lead to childhood obesity in a prospective cohort study?

BACKGROUND

Some studies show that greater parental control over children's eating habits predicts later obesity, but it is unclear whether parents are reacting to infants who are already overweight.

OBJECTIVE

To examine the longitudinal association between maternal feeding restriction at age 1 and body mass index (BMI) at age 3 and the extent to which the association is explained by weight for length (WFL) at age 1.

METHODS

We studied 837 mother-infant pairs from a prospective cohort study. The main exposure was maternal feeding restriction at age 1, defined as agreeing or strongly agreeing with the following question: "I have to be careful not to feed my child too much." We ran multivariable linear regression models before and after adjusting for WFL at age 1. All models were adjusted for parental and child sociodemographic characteristics.

RESULTS

100 (12.0%) mothers reported feeding restriction at age 1. Mean (SD) WFL z-score at age 1 was 0.32 (1.01), and BMI z-score at age 3 was 0.43 (1.01). Maternal feeding restriction at age 1 was associated with higher BMI z-score at age 3 before (β 0.26 (95% CI 0.05 to 0.48)) but not after (β 0.00 (95% CI -0.17 to 0.18)) adjusting for WFL z-score at age 1. Each unit of WFL z-score at age 1 was associated with an increment of 0.57 BMI z-score units at age 3 (95% CI 0.51 to 0.62).

CONCLUSIONS

We found that maternal feeding restriction was associated with children having a higher BMI at age 3 before, but not after, adjusting for WFL at age 1. One potential reason may be that parents restrict the food intake of infants who are already overweight.

Proteomic analysis reveals virus-specific Hsp25 modulation in cardiac myocytes

Viruses frequently infect the heart but clinical myocarditis is rare, suggesting that the cardiac antiviral response is uniquely effective. Indeed, the Type I interferon (IFN) response is cardiac cell-type specific and provides one integrated network of protection for the heart. Here, a proteomic approach was used to identify additional proteins that may be involved in the cardiac antiviral response. Reovirus-induced murine myocarditis reflects direct viral damage to cardiac cells and offers an excellent system for study. Primary cultures of murine cardiac myocytes were infected with myocarditic or nonmyocarditic reovirus strains, and whole cell lysates were compared by two-dimensional difference gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF/TOF) tandem mass spectrometry. Results were quantitative and reproducible and demonstrated that whole proteome changes clustered according to viral pathogenic phenotype. Moreover, the data suggest that the heat shock protein Hsp25 is modulated differentially by myocarditic and nonmyocarditic reoviruses and may play a role in the cardiac antiviral response. Members of seven virus families modulate Hsp25 or Hsp27 expression in a variety of cell types, suggesting that Hsp25 participation in the antiviral response may be widespread. However, results here provide the first evidence for a virus-induced decrease in Hsp25/27 and suggest that viruses may have evolved a mechanism to subvert this protective response, as they have for IFN.

Rotavirus and reovirus modulation of the interferon response

The mammalian reoviruses and rotaviruses have evolved specific mechanisms to evade the Type I interferon (IFN) antiviral response. Rotavirus likely represses the IFN response by at least 4 mechanisms. First, the rotavirus protein NSP1, most likely functioning as an E3 ligase, can induce proteasome-dependent degradation of the transcription factors IRF3, IRF5, and IRF7 to prevent their induction of IFN. Second, NSP1 can induce proteasome-dependent degradation of the ubiquitin ligase complex protein beta-TrCP, resulting in stabilization of I kappaB and concomitant failure of virus to activate NF-kappaB for induction of IFN. Third, rotavirus may sequester NF-kappaB in viroplasms. And fourth, rotavirus can prevent STAT1 and STAT2 nuclear translocation. The predominant mechanism for rotavirus inhibition of the IFN response is likely both rotavirus strain-specific and cell type-specific. The mammalian reoviruses also display strain-specific differences in their modulation of the IFN response. Reovirus activates RIG-I and IPS-1 for phosphorylation of IRF3. Reovirus-induced activation of MDA5 also participates in induction if IFN-beta, perhaps through activation of NF-kappaB. Reovirus likely inhibits the IFN response by at least 3 virus strain-specific mechanisms. First, the reovirus mu2 protein can induce an unusual nuclear accumulation of IRF9 and repress IFN-stimulated gene (ISG) expression, most likely by disrupting IRF9 function as part of the heterotrimeric transcription factor complex, ISGF3. Second, the reovirus sigma 3 protein can bind dsRNA and prevent activation of the latent antiviral effector protein PKR. And third, genetic approaches have identified the reovirus lambda 2 and sigma 2 proteins in virus strain-specific modulation of the IFN response, but the significance remains unclear. In sum, members of the family Reoviridae have evolved a variety of mechanisms to subvert the host's innate protective response.

IFN-alpha expression and antiviral effects are subtype and cell type specific in the cardiac response to viral infection

The interferon-beta (IFN-beta) response is critical for protection against viral myocarditis in several mouse models, and IFN-alpha or -beta treatment is beneficial against human viral myocarditis. The IFN-beta response in cardiac myocytes and cardiac fibroblasts forms an integrated network for organ protection; however, the different IFN-alpha subtypes have not been studied in cardiac cells. We developed a quantitative RT-PCR assay that distinguishes between 13 highly conserved IFN-alpha subtypes and found that reovirus T3D induces five IFN-alpha subtypes in primary cardiac myocyte and fibroblast cultures: IFN-alpha1, -alpha2, -alpha4, -alpha5, and -alpha8/6. Murine IFN-alpha1, -alpha2, -alpha4, or -alpha5 treatment induced IRF7 and ISG56 and inhibited reovirus T3D replication in both cell types. This first investigation of IFN-alpha subtypes in cardiac cells for any virus demonstrates that IFN-alpha is induced in cardiac cells, that it is both subtype and cell type specific, and that it is likely important in the antiviral cardiac response.

Cholinergic agonists regulate JAK2/STAT3 signaling to suppress endothelial cell activation

The cholinergic anti-inflammatory pathway is a physiological mechanism that inhibits cytokine production and minimizes tissue injury during inflammation. Previous investigations revealed that cholinergic stimulation (via cholinergic agonists and vagus nerve stimulation) suppresses endothelial cell activation and leukocyte recruitment. The purpose of this study was to investigate the mechanisms by which cholinergic agonists (e.g., nicotine and GTS-21) regulate endothelial cell activation. Specifically, we examined the effects of cholinergic agonists on IL-6-mediated endothelial cell activation through the JAK2/STAT3 signaling pathway. Treatment of macrovascular human umbilical vein endothelial cells (HUVECs) and microvascular endothelial cells (MVECs) with the cholinergic agonists nicotine and GTS-21 significantly reduced IL-6-mediated monocyte chemoattractant protein-1 (MCP-1) production and ICAM-1 expression which are regulated through the JAK2/STAT3 pathway. We found that treatment of endothelial cells with cholinergic agonists significantly reduced STAT3 activation by phosphorylation and DNA binding. The inhibition of STAT3 phosphorylation was reversed by sodium orthovanadate, an inhibitor of tyrosine phosphatases, as well as by NSC-87877 suggesting a SHP1/2-dependent mechanism. Further investigations showed that cholinergic agonists reduced the phosphorylation of JAK2, an upstream component of the JAK2/STAT3 pathway. Finally, we observed that nicotine and GTS-21 treatment decreased levels of SOCS3 (suppressor of cytokine signaling; a regulator of the inflammatory activity of IL-6) in activated endothelial cells. These data demonstrate that cholinergic agonists suppress IL-6-mediated endothelial cell activation through the JAK2/STAT3 pathway. Our results have significant implications for better understanding the therapeutic potential of cholinergic agonists for treating IL-6 mediated inflammatory conditions.

Dysregulated chemokine receptor expression and chemokine-mediated cell trafficking in pediatric patients with ESRD

BACKGROUND AND OBJECTIVES

Children and adolescents with ESRD on dialysis are susceptible to serious bacterial infections (SBI). Chemokines and chemokine receptors play a critical role in modulating macrophage and neutrophil function. This study examined the hypothesis that expression and/or function of these molecules is dysregulated in patients with ESRD, contributing to leukocyte dysfunction. Design setting, participants, & measurements: Pediatric patients, age 6 mo to 18 yr, with ESRD treated with either hemodialysis or peritoneal dialysis were enrolled in this prospective, nontherapeutic study. Blood was collected for plasma chemokine levels, chemokine receptor profiling by flow cytometry, and functional chemotaxis studies on neutrophils and mononuclear cells.

RESULTS

ESRD in children was associated with reduced expression of the chemokine receptors CXCR1 and chemokine (C-C motif) receptor 2 (CCR2) on circulating neutrophils and monocytes, respectively. When ESRD patients were divided into two subgroups, those who were infection-free and those who had three or more SBI in the preceding year, the differences in chemokine receptor expression were statistically significant compared with control subjects only in those with recurrent infection. In addition to the effects of ESRD on baseline chemokine receptor expression, the hemodialysis procedure itself acutely lowered neutrophil CXCR1 and monocyte CCR2 expression. Furthermore, neutrophil and monocyte responsiveness to chemokine-mediated trafficking signals was impaired in all ESRD patients studied. This abnormality was independent of the level of chemokine receptor expression on the leukocytes.

CONCLUSIONS

The data presented in this study suggest that chemokine receptor dysregulation contributes to leukocyte dysfunction in patients with ESRD. This alteration is especially prominent in ESRD patients with recurrent infection.

Modulation of rat intestinal nuclear factor NF-kappaB by gum arabic

The objective of this study was to test the hypothesis that in an animal model of cathartic-induce intestinal dysfunction the proabsorptive effects of gum arabic (GA) could be associated with modulation of nuclear factor-kappaB (NF-kappaB) and with reduction of the inflammatory response caused by cathartics, as evidenced by intestinal mucosa cytokine production and gene expression. Juvenile male rats were given a phenolphthalein-magnesium citrate solution for 6 days, by itself or supplemented with either 10 or 20 g L(-1) GA, as a sole source of fluid. The controls given were tap water alone or with added 20 g L(-1) GA. The animals were euthanized and small-intestinal mucosa nuclear fractions and RNA were isolated. NF-kappaB p65 activity was highest after administration of cathartics, lowest in controls, and intermediate in GA-treated rats. Mucosal IL-1beta was overexpressed in tissues from cathartic-treated rats and from rats given high-GA solutions. Gene-array analysis revealed a complex pattern of gene regulation by cathartics which selectively upregulated several subfamilies of cytochrome P-450 family 2 genes. Co-administration of GA did not block this effect. These findings suggest that local anti-inflammatory effects on the small intestine could be obtained by administration of a nonabsorbable proteoglycan such as GA.

Functional analysis of Leishmania major cyclophilin

A potent immunosuppressive drug cyclosporin A (CsA) is known to inhibit human cell infection by the pathogenic protozoan parasite Leishmania major both in vitro and in vivo. The proposed mechanism of action involves CsA binding to Leishmania major-expressed cyclophilin and subsequent down-regulation of signaling events necessary for establishing productive infection. Recently, we identified a ubiquitously expressed membrane protein, CD147, as a signaling receptor for extracellular cyclophilins in mammalian cells. Here we demonstrate that, while being enzymatically active, the Leishmania cyclophilin, unlike its human homologue, does not interact with CD147 on the cell surface of target cells. CD147 facilitates neither Leishmania binding nor infection. Primary structure and biochemical analyses revealed that the parasite's cyclophilin is defective in heparan binding, an event required for signaling interaction between CD147 and human cyclophilin. When the heparan-binding motif was reconstituted in Leishmania cyclophilin, it regained the CD147-dependent signaling activity. These results underscore a critical role of cyclophilin-heparan interactions in CD147-mediated signaling events and argue against the role of Leishmania cyclophilin in parasite binding to target cells.

Retinoic acid-inducible gene-I and interferon-beta promoter stimulator-1 augment proapoptotic responses following mammalian reovirus infection via interferon regulatory factor-3

During viral infection, cells initiate antiviral responses to contain replication and inhibit virus spread. One protective mechanism involves activation of transcription factors interferon regulatory factor-3 (IRF-3) and NF-kappaB, resulting in secretion of the antiviral cytokine, interferon-beta. Another is induction of apoptosis, killing the host cell before virus disseminates. Mammalian reovirus induces both interferon-beta and apoptosis, raising the possibility that both pathways are initiated by a common cellular sensor. We show here that reovirus activates IRF-3 with kinetics that parallel the activation of NF-kappaB, a known mediator of reovirus-induced apoptosis. Activation of IRF-3 requires functional retinoic acid inducible gene-I and interferon-beta promoter stimulator-1, but these intracellular sensors are dispensable for activation of NF-kappaB. Interferon-beta promoter stimulator-1 and IRF-3 are required for efficient apoptosis following reovirus infection, suggesting a common mechanism of antiviral cytokine induction and activation of the cell death response.

The arthritis severity quantitative trait loci Cia4 and Cia6 regulate neutrophil migration into inflammatory sites and levels of TNF-alpha and nitric oxide

Neutrophils are required for the development of arthritis, and their migration into the synovial tissue coincides with the onset of clinical disease. Synovial neutrophil numbers also correlate with rheumatoid arthritis disease activity and severity. We hypothesized that certain arthritis severity genes regulate disease via the regulation of neutrophil migration into the joint. This hypothesis was tested in the synovial-like air pouch model injected with carrageenan using arthritis-susceptible DA and arthritis-resistant F344 rats. DA had nearly 3-fold higher numbers of exudate neutrophils compared with F344 (p < 0.001). Five DA.F344(QTL) strains congenic for severity loci and protected from autoimmune arthritis were studied. Only DA.F344(Cia4) (chromosome 7) and DA.F344(Cia6) (chromosome 8) congenics had significantly lower exudate neutrophil counts compared with DA. TNF-alpha levels were 2.5-fold higher in DA exudates as compared with F344 exudates, and that difference was accounted for by the Cia4 locus. Exudate levels of NO, a known inhibitor of neutrophil chemotaxis, were higher in F344, compared with DA, and that difference was accounted for by Cia6. This is the first time that non-MHC autoimmune arthritis loci are found to regulate three central components of the innate immune response implicated in disease pathogenesis, namely neutrophil migration into an inflammatory site, as well as exudate levels of TNF-alpha and NO. These observations underscore the importance of identifying the Cia4 and Cia6 genes, and suggest that they should generate useful novel targets for development of new therapies.

The arthritis severity quantitative trait locus Cia7 regulates neutrophil migration into inflammatory sites

Neutrophils are required for the development of arthritis in rodents, and are the predominant cell in the synovial fluid of active rheumatoid arthritis. We hypothesized that neutrophil migration into the inflammed joint is genetically regulated. In addition, this genetic regulation would be accounted for by one of the arthritis loci that we have previously identified in an intercross between arthritis-susceptible DA and arthritis-resistant ACI rats studied for collagen-induced arthritis. We used the synovial-like air pouch model injected with carrageenan, and tested DA, ACI, and four congenic strains. ACI exudates had a significantly lower number of neutrophils compared with DA. Transfer of DA alleles at Cia7 into the ACI background, as in ACI.DA(Cia7) congenics, was enough to increase exudate neutrophil numbers to levels identical to DA, and this locus accounted for the difference between parental strains. None of the other congenic intervals explained the differences in exudate neutrophil counts. In conclusion, we have identified a novel function for Cia7, and determined that it regulates neutrophil migration into a synovial-like inflammatory site. Our data revealed no intrinsic defect in neutrophil responses to chemotactic agents, and suggest that Cia7 regulates an as yet unidentified factor central to neutrophil recruitment into inflammed tissues.

Food behaviors and other strategies to prevent and treat pediatric overweight

OBJECTIVE

To summarize the evidence for the following six strategies to prevent or treat overweight among children: promoting breastfeeding, promoting physical activity, reducing TV/video viewing, increasing fruit and vegetable consumption, reducing sugar-sweetened drink consumption, and reducing portion sizes.

METHODS

Summarization of the relevant literature including review articles, relevant newly published work, the Institute of Medicine's Report on Preventing Childhood Obesity and the Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity, 2001. This is not a comprehensive review.

RESULTS

Evidence for the association between each strategy and overweight varies. For breastfeeding, physical activity, and TV viewing, there are large review studies. Breastfed children may have a small reduction in risk for overweight. Participation in physical activity may reduce the risk of overweight among school-aged children and adolescents. For preschool- and school-aged children, reducing TV viewing time may reduce their risk of overweight, but most studies report small significant associations. Evidence for an association between each dietary factor and overweight is limited and inconclusive. The biggest gaps in evidence are for the effectiveness of interventions using these strategies. The reviewed interventions based on increasing physical activity (n=7) were effective. Two randomized trials suggest that reducing TV viewing reduces overweight. No intervention studies were found that examined the effectiveness of changing fruit and vegetable consumption, sugar-sweetened drink consumption, or portion sizes. Further clarification of the effect of breastfeeding on obesity is needed.

CONCLUSIONS

These six strategies are reasonable ways to attempt prevention or treatment of overweight in children. Strength of the evidence varies by strategy. The key finding is that more applied research is needed to determine the effectiveness of these and other strategies.

Role of HMGB1 in apoptosis-mediated sepsis lethality

Severe sepsis, a lethal syndrome after infection or injury, is the third leading cause of mortality in the United States. The pathogenesis of severe sepsis is characterized by organ damage and accumulation of apoptotic lymphocytes in the spleen, thymus, and other organs. To examine the potential causal relationships of apoptosis to organ damage, we administered Z-VAD-FMK, a broad-spectrum caspase inhibitor, to mice with sepsis. We found that Z-VAD-FMK–treated septic mice had decreased levels of high mobility group box 1 (HMGB1), a critical cytokine mediator of organ damage in severe sepsis, and suppressed apoptosis in the spleen and thymus. In vitro, apoptotic cells activate macrophages to release HMGB1. Monoclonal antibodies against HMGB1 conferred protection against organ damage but did not prevent the accumulation of apoptotic cells in the spleen. Thus, our data indicate that HMGB1 production is downstream of apoptosis on the final common pathway to organ damage in severe sepsis.

Redox regulation of cyclophilin A by glutathionylation

Using redox proteomics techniques to characterize the thiol status of proteins in human T lymphocytes, we identified cyclophilin A (CypA) as a specifically oxidized protein early after mitogen activation. CypA is an abundantly expressed cytosolic protein, target of the immunosuppressive drug cyclosporin A (CsA), for which a variety of functions has been described. In this study, we could identify CypA as a protein undergoing glutathionylation in vivo. Using MALDI-MS we identified Cys52 and Cys62 as targets of glutathionylation in T lymphocytes, and, using bioinformatic tools, we defined the reasons for the susceptibility of these residues to the modification. In addition, we found by circular dichroism spectroscopy that glutathionylation has an important impact on the secondary structure of CypA. Finally, we suggest that glutathionylation of CypA may have biological implications and that CypA may play a key role in redox regulation of immunity.

Organ-specific roles for transcription factor NF-kappaB in reovirus-induced apoptosis and disease

Reovirus induces apoptosis in cultured cells and in vivo. In cell culture models, apoptosis is contingent upon a mechanism involving reovirus-induced activation of transcription factor NF-kappaB complexes containing p50 and p65/RelA subunits. To explore the in vivo role of NF-kappaB in this process, we tested the capacity of reovirus to induce apoptosis in mice lacking a functional nfkb1/p50 gene. The genetic defect had no apparent effect on reovirus replication in the intestine or dissemination to secondary sites of infection. In comparison to what was observed in wild-type controls, apoptosis was significantly diminished in the CNS of p50-null mice following reovirus infection. In sharp contrast, the loss of p50 was associated with massive reovirus-induced apoptosis and uncontrolled reovirus replication in the heart. Levels of IFN-beta mRNA were markedly increased in the hearts of wild-type animals but not p50-null animals infected with reovirus. Treatment of p50-null mice with IFN-beta substantially diminished reovirus replication and apoptosis, which suggests that IFN-beta induction by NF-kappaB protects against reovirus-induced myocarditis. These findings reveal an organ-specific role for NF-kappaB in the regulation of reovirus-induced apoptosis, which modulates encephalitis and myocarditis associated with reovirus infection.

Role of Rho family GTPases in CCR1- and CCR5-induced actin reorganization in macrophages

The beta-chemokines, MIP-1alpha/CCL3, MIP-1beta/CCL4, and RANTES/CCL5, play a critical role in the selective accumulation and activation of macrophages in inflamed tissues. Herein, we demonstrate that the binding of each of these beta-chemokines to their cognate receptors, CCR1 and CCR5, in either macrophages or in CCR1- or CCR5-transfected CHO cells, induced actin reorganization and the formation of lamellipodia that are characteristic of the activation of the Rho family GTPase, Rac. A dominant negative mutant of Rac, but not dominant negative mutants of RhoA or Cdc42, blocked MIP-1alpha-induced lamellipodia formation. Moreover, this MIP-1alpha-induced Rac activation and consequent lamellipodia formation is Gi- and phosphoinositide-3 kinase (PI3K)-mediated. Thus, Rac activation is critical for both CCR1- and CCR5-triggered signaling cascades mediating beta-chemokine-induced reorganization of the actin cytoskeleton, a process essential for effective recruitment and activation of macrophages in inflammation.

Cell surface expression of CD147/EMMPRIN is regulated by cyclophilin 60

CD147, also known as extracellular matrix metalloproteinase inducer, is a regulator of matrix metalloproteinase production and also serves as a signaling receptor for extracellular cyclophilins. Previously, we demonstrated that cell surface expression of CD147 is sensitive to cyclophilin-binding drug cyclosporin A, suggesting involvement of a cyclophilin in the regulation of intracellular transport of CD147. In this report, we identify this cyclophilin as cyclophilin 60 (Cyp60), a distinct member of the cyclophilin family of proteins. CD147 co-immunoprecipitated with Cyp60, and confocal immunofluorescent microscopy revealed intracellular co-localization of Cyp60 and CD147. This interaction with Cyp60 involved proline 211 of CD147, which was shown previously to be critical for interaction between CD147 and another cyclophilin, cyclophilin A, in solution. Mutation of this proline residue abrogated co-immunoprecipitation of CD147 and Cyp60 and reduced surface expression of CD147 on the plasma membrane. Suppression of Cyp60 expression using RNA interference had an effect similar to that of cyclosporin A: reduction of cell surface expression of CD147. These results suggest that Cyp60 plays an important role in the translocation of CD147 to the cell surface. Therefore, Cyp60 may present a novel target for therapeutic interventions in diseases where CD147 functions as a pathogenic factor, such as cancer, human immunodeficiency virus infection, or rheumatoid arthritis.

Cholinergic stimulation blocks endothelial cell activation and leukocyte recruitment during inflammation

Endothelial cell activation plays a critical role in regulating leukocyte recruitment during inflammation and infection. Based on recent studies showing that acetylcholine and other cholinergic mediators suppress the production of proinflammatory cytokines via the α7 nicotinic acetylcholine receptor (α7 nAChR) expressed by macrophages and our observations that human microvascular endothelial cells express the α7 nAChR, we examined the effect of cholinergic stimulation on endothelial cell activation in vitro and in vivo. Using the Shwartzman reaction, we observed that nicotine (2 mg/kg) and the novel cholinergic agent CAP55 (12 mg/kg) inhibit endothelial cell adhesion molecule expression. Using endothelial cell cultures, we observed the direct inhibitory effects of acetylcholine and cholinergic agents on tumor necrosis factor (TNF)-induced endothelial cell activation. Mecamylamine, an nAChR antagonist, reversed the inhibition of endothelial cell activation by both cholinergic agonists, confirming the antiinflammatory role of the nAChR cholinergic pathway. In vitro mechanistic studies revealed that nicotine blocked TNF-induced nuclear factor–κB nuclear entry in an inhibitor κB (IκB)α- and IκBɛ-dependent manner. Finally, with the carrageenan air pouch model, both vagus nerve stimulation and cholinergic agonists significantly blocked leukocyte migration in vivo. These findings identify the endothelium, a key regulator of leukocyte trafficking during inflammation, as a target of anti-inflammatory cholinergic mediators.

Macrophage inflammatory protein 1alpha inhibits postentry steps of human immunodeficiency virus type 1 infection via suppression of intracellular cyclic AMP

Primary isolates of human immunodeficiency virus type 1 (HIV-1) predominantly use chemokine receptor CCR5 to enter target cells. The natural ligands of CCR5, the beta-chemokines macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, and RANTES, interfere with HIV-1 binding to CCR5 receptors and decrease the amount of virions entering cells. Although the inhibition of HIV-1 entry by beta-chemokines is well documented, their effects on postentry steps of the viral life cycle and on host cell components that control the outcome of infection after viral entry are not well defined. Here, we show that all three beta-chemokines, and MIP-1alpha in particular, inhibit postentry steps of the HIV-1 life cycle in primary lymphocytes, presumably via suppression of intracellular levels of cyclic AMP (cAMP). Productive HIV-1 infection of primary lymphocytes requires cellular activation. Cell activation increases intracellular cAMP, which is required for efficient synthesis of proviral DNA during early steps of viral infection. Binding of MIP-1alpha to cognate receptors decreases activation-induced intracellular cAMP levels through the activation of inhibitory G proteins. Furthermore, inhibition of one of the downstream targets of cAMP, cAMP-dependent PKA, significantly inhibits synthesis of HIV-1-specific DNA without affecting virus entry. These data reveal that beta-chemokine-mediated inhibition of virus replication in primary lymphocytes combines inhibitory effects at the entry and postentry levels and imply the involvement of beta-chemokine-induced signaling in postentry inhibition of HIV-1 infection.

Regulation of CD147 Cell Surface Expression

CD147, also known as extracellular matrix metalloproteinase inducer, is a regulator of matrix metalloproteinase production and serves as a signaling receptor for extracellular cyclophilins. Here we demonstrate that the cell surface expression of CD147 is regulated by cyclophilins via the transmembrane domain of CD147. Solution binding experiments demonstrated that the transmembrane domain was both necessary and sufficient for CD147 binding to cyclophilin A (CypA). Treatment with cyclosporin A significantly reduced surface expression of CD147 and of CD8-CD147 fusion protein carrying the extracellular domain of CD8 fused to the transmembrane and cytoplasmic domains of CD147, but did not affect expression of CD8. Peptide binding studies demonstrated specific interaction between CypA and the proline-containing peptide from the CD147 transmembrane domain. Mutation of this proline residue reduced binding of CD147-derived peptides to CypA and also diminished transport of CD147 to the plasma membrane without reducing the total level of CD147 expression. These results suggest involvement of a cyclophilin-related protein in CD147 cell surface expression and provide molecular details for regulation of CD147 trafficking by cyclophilins.

Basal and reovirus-induced beta interferon (IFN-beta) and IFN-beta-stimulated gene expression are cell type specific in the cardiac protective response

Viral myocarditis is an important human disease, with a wide variety of viruses implicated. Cardiac myocytes are not replenished yet are critical for host survival and thus may have a unique response to infection. Previously, we determined that the extent of reovirus induction of beta interferon (IFN-beta) and IFN-beta-mediated protection in primary cardiac myocyte cultures was inversely correlated with the extent of reovirus-induced cardiac damage in a mouse model. Surprisingly, and in contrast, the IFN-beta response did not determine reovirus replication in skeletal muscle cells. Here we compared the IFN-beta response in cardiac myocytes to that in primary cardiac fibroblast cultures, a readily replenished cardiac cell type. We compared basal and reovirus-induced expression of IFN-beta, IRF-7 (an interferon-stimulated gene [ISG] that further induces IFN-beta), and another ISG (561) in the two cell types by using real-time reverse transcription-PCR. Basal IFN-beta, IRF-7, and 561 expression was higher in cardiac myocytes than in cardiac fibroblasts. Reovirus T3D induced greater expression of IFN-beta in cardiac myocytes than in cardiac fibroblasts but equivalent expression of IRF-7 and 561 in the two cell types (though fold induction for IRF-7 and 561 was higher in fibroblasts than in myocytes because of the differences in basal expression). Interestingly, while reovirus replicated to equivalent titers in cardiac myocytes and cardiac fibroblasts, removal of IFN-beta resulted in 10-fold-greater reovirus replication in the fibroblasts than in the myocytes. Together the data suggest that the IFN-beta response controls reovirus replication equivalently in the two cell types. In the absence of reovirus-induced IFN-beta, however, reovirus replicates to higher titers in cardiac fibroblasts than in cardiac myocytes, suggesting that the higher basal IFN-beta and ISG expression in myocytes may play an important protective role.

Ethanol blocks leukocyte recruitment and endothelial cell activation in vivo and in vitro

Immune system impairment and increased susceptibility to infection among alcohol abusers is a significant but not well-understood problem. We hypothesized that acute ethanol administration would inhibit leukocyte recruitment and endothelial cell activation during inflammation and infection. Using LPS and carrageenan air pouch models in mice, we found that physiological concentrations of ethanol (1-5 g/kg) significantly blocked leukocyte recruitment (50-90%). Because endothelial cell activation and immune cell-endothelial cell interactions are critical regulators of leukocyte recruitment, we analyzed the effect of acute ethanol exposure on endothelial cell activation in vivo using the localized Shwartzman reaction model. In this model, ethanol markedly suppressed leukocyte accumulation and endothelial cell adhesion molecule expression in a dose-dependent manner. Finally, we examined the direct effects of ethanol on endothelial cell activation and leukocyte-endothelial cell interactions in vitro. Ethanol, at concentrations within the range found in human blood after acute exposure and below the levels that induce cytotoxicity (0.1-0.5%), did not induce endothelial cell activation, but significantly inhibited TNF-mediated endothelial cell activation, as measured by adhesion molecule (E-selectin, ICAM-1, VCAM-1) expression and chemokine (IL-8, MCP-1, RANTES) production and leukocyte adhesion in vitro. Studies exploring the potential mechanism by which ethanol suppresses endothelial cell activation revealed that ethanol blocked NF-kappaB nuclear entry in an IkappaBalpha-dependent manner. These findings support the hypothesis that acute ethanol overexposure may increase the risk of infection and inhibit the host inflammatory response, in part, by blocking endothelial cell activation and subsequent immune cell-endothelial cell interactions required for efficient immune cell recruitment.

Caspase inhibition protects against reovirus-induced myocardial injury in vitro and in vivo

Viral myocarditis is a disease with a high morbidity and mortality. The pathogenesis of this disease remains poorly characterized, with components of both direct virus-mediated and secondary inflammatory and immune responses contributing to disease. Apoptosis has increasingly been viewed as an important mechanism of myocardial injury in noninfectious models of cardiac disease, including ischemia and failure. Using a reovirus murine model of viral myocarditis, we characterized and targeted apoptosis as a key mechanism of virus-associated myocardial injury in vitro and in vivo. We demonstrated caspase-3 activation, in conjunction with terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling and annexin binding, in cardiac myocytes after myocarditic viral infection in vitro. We also demonstrated a tight temporal and geographical correlation between caspase-3 activation, histologic injury, and viral load in cardiac tissue after myocarditic viral infection in vivo. Two pharmacologic agents that broadly inhibit caspase activity, Q-VD-OPH and Z-VAD(OMe)-FMK, effectively inhibited virus-induced cellular death in vitro. The inhibition of caspase activity in vivo by the use of pharmacologic agents as well as genetic manipulation reduced virus-induced myocardial injury by 40 to 60% and dramatically improved survival in infected caspase-3-deficient animals. This study indicates that apoptosis plays a critical role in mediating cardiac injury in the setting of viral myocarditis and is the first demonstration that caspase inhibition may serve as a novel therapeutic strategy for this devastating disease.