Soluble CD14 activates monocytic cells independently of lipopolysaccharide

Proteomic research on new urinary biomarkers of renal disease in canine leishmaniosis: Survival and monitoring response to treatment

The objective of our study was to search for survival biomarkers (SB) and treatment response monitoring biomarkers (TRMB) in the urinary proteome of dogs with renal disease secondary to canine leishmaniosis (CanL), using UHPLC-MS/MS. The proteomic data are available via ProteomeXchange with identifier PXD042578. Initially, a group of 12 dogs was evaluated and divided into survivors (SG; n = 6) and nonsurvivors (NSG; n = 6). A total of 972 proteins were obtained from the evaluated samples. Then, bioinformatic analysis reduced them to 6 proteins like potential SB increased in the NSG, specifically, Haemoglobin subunit Alpha 1, Complement Factor I, Complement C5, Fibrinogen beta chain (fragment), Peptidase S1 domain-containing protein, and Fibrinogen gamma chain. Afterwards, SG was used to search for TRMB, studying their urine at 0, 30, and 90 days, and 9 proteins that decreased after treatment were obtained: Apolipoprotein E, Cathepsin B, Cystatin B, Cystatin-C-like, Lysozyme, Monocyte differentiation CD14, Pancreatitis-associated precursor protein, Profilin, and Protein FAM3C. Finally, enrichment analysis provided information about the biological mechanisms in which these proteins are involved. In conclusion, this study provides 15 new candidate urinary biomarkers and an improved understanding of the pathogenesis of kidney disease in CanL.

CD14 signaling mediates lung immunopathology and mice mortality induced by Achromobacter xylosoxidans

Objective and design

Our research aimed to investigate the role of CD14 in pulmonary infection by Achromobacter xylosoxidans in an experimental murine model.

Methods

C57Bl/6 or CD14-deficient mice were infected intratracheally with non-lethal inoculum of A. xylosoxidans. At times 1, 3 and 7 days after infection, lungs, bronchoalveolar lavage and blood were collected. CD14 gene expression was determined by RT-PCR. The bacterial load in the lungs was assessed by counting colony forming units (CFU). Cytokines, chemokines, lipocalin-2 and sCD14 were quantified by the ELISA method. Inflammatory infiltrate was observed on histological sections stained with HE, and leukocyte subtypes were assessed by flow cytometry. In another set of experiments, C57Bl/6 or CD14-deficient mice were inoculated with lethal inoculum and the survival rate determined.

Results

CD14-deficient mice are protected from A. xylosoxidans-induced death, which is unrelated to bacterial load. The lungs of CD14-deficient mice presented a smaller area of tissue damage, less neutrophil and macrophage infiltration, less pulmonary edema, and a lower concentration of IL-6, TNF-α, CXCL1, CCL2 and CCL3 when compared with lungs of C57Bl/6 mice. We also observed that A. xylosoxidans infection increases the number of leukocytes expressing mCD14 and the levels of sCD14 in BALF and serum of C57Bl/6-infected mice.

Conclusions

In summary, our data show that in A. xylosoxidans infection, the activation of CD14 induces intense pulmonary inflammatory response resulting in mice death.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00011-022-01641-8.

Elevated Plasma Levels of sCD14 and MCP-1 Are Associated With HIV Associated Neurocognitive Disorders Among Antiretroviral-Naive Individuals in Nigeria

BACKGROUND

Mononuclear cells play key roles in the pathogenesis of HIV-associated neurocognitive disorders (HAND). Limited studies have looked at the association of markers of monocyte activation with HAND in Africa. We examined this association among HIV-1-infected patients in Nigeria.

METHOD

A total of 190 HIV-infected treatment-naive participants with immune marker data were included in this cross-sectional study. Plasma levels of soluble CD14 (sCD14), soluble CD163, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), and neopterin were measured. Demographically adjusted T scores obtained from a 7-domain neuropsychological test battery were generated, and functional status was assessed using activities of daily living questionnaire. Participants were classified as unimpaired, having asymptomatic neurocognitive impairment (ANI), mild neurocognitive disorder (MND), or HIV-associated dementia (HAD) in line with the "Frascati" criteria.

RESULTS

Thirty-two participants (16.8%) had ANI, 14 (7.4%) had MND, whereas none had HAD. In multivariable linear regression analyses, after adjusting for age, gender, education, CD4 count, and viral load, mean levels of sCD14 were higher among those with ANI and MND as compared with the unimpaired (P = 0.033 and 0.023, respectively). Similarly, the mean level of MCP-1 was greater among those with HAND as compared with the unimpaired (P = 0.047). There were also trends for higher levels of sCD163 and TNF-α among females with MND in univariable analyses.

CONCLUSIONS

Levels of monocyte activation markers correlate with the severity of impairment among individuals with HAND. The mechanisms that underlie these effects and the potential role of gender require further study.

Different phenotypes of non-classical monocytes associated with systemic inflammation, endothelial alteration and hepatic compromise in patients with dengue

Although dengue can progress to severe stages, the exact causes of this phenomenon are unknown; however, the possibility of monocyte participation is acknowledged. It has been suggested that monocyte subsets (classical, intermediate and non-classical) play differential roles in dengue immunopathology. Therefore, we determined the count of monocyte subsets and obtained the clinical information of patients with dengue. We noted a significant decrease in the count of non-classical monocytes in patients compared with controls. With this finding, we focused on studying the phenotype of non-classical monocytes in the present study. An increase in activation and differentiation markers, such as CD64, CD86, the percentage of tumor necrosis factor-α⁺ cells and exposure of phosphatidylserine, were recorded in the non-classical monocytes of patients compared with controls. Moreover, a significant decrease in the expression of CX3CR1 with a corresponding increase in the expressions of CCR2, CCR5, CD11b and CD54 was detected in the non-classical monocytes of patients in comparison with that of the controls. Significant increases in the frequency of microparticles from endothelium and in the concentrations of interleukin-6 (IL-6), IL-8 and IL-10 were noted in the plasma of patients. These findings demonstrate that in patients with dengue, non-classical monocytes are activated, exhibiting a phenotype associated with more differentiation, produces tumor necrosis factor-α and has a profile of less endothelial surveillance closer to the cellular migration. These changes were associated with hepatic compromise, endothelial alteration and high concentration of circulating cytokines. Hence, alterations of non-classical monocytes seem to be associated with the immunopathology of dengue infection.

Molecular Camouflage of Plasmodium falciparum Merozoites by Binding of Host Vitronectin to P47 Fragment of SERA5

The malaria parasite Plasmodium falciparum proliferates in the blood stream where the host immune system is most active. To escape from host immunity, P. falciparum has developed a number of evasion mechanisms. Serine repeat antigen 5 (SERA5) is a blood stage antigen highly expressed at late trophozoite and schizont stages. The P47 N-terminal domain of SERA5, the basis of SE36 antigen of the blood stage vaccine candidate under clinical trials, covers the merozoite surface. Exploring the role of the P47 domain, screening of serum proteins showed that vitronectin (VTN) directly binds to 20 residues in the C-terminal region of SE36. VTN co-localized with P47 domain in the schizont and merozoite stages. Phagocytosis assay using THP-1 cells demonstrated that VTN bound to SE36 prevented engulfment of SE36-beads. In addition, several serum proteins localized on the merozoite surface, suggesting that host proteins camouflage merozoites against host immunity via binding to VTN.

Engagement of CD14 sensitizes primary monocytes to IFN-γ to produce IL-12/23p40 and IL-23 through p38 mitogen-activated protein kinase and independent of the janus kinase/signal transducers and activators of transcription signaling

Interferon (IFN)-γ is a potent stimulator of the IL-12 family Th1 cytokines, including IL-12/23p40 and IL-23, responsible for coordinating the innate and adaptive immune responses. Our results show that IFN-γ induced the production of IL-12/23p40 and IL-23p19 mRNA as well as IL-12p40 and IL-23 proteins in primary human monocytes isolated by positive selection through anti-CD14 microbeads. These results were confirmed by IFN-γ stimulation of CD14-activated monocytes resulting in IL-12/23p40 and IL-23 production. We investigated the signaling pathways governing the regulation of IL-23 and its subunits IL-23p40 and IL-23p19 following IFN-γ stimulation. We observed a differential regulation of IL-23p19, IL-12/23p40, and IL-23 following IFN-γ stimulation. IFN-γ-induced IL-23 and IL-12/23p40 expression was positively regulated by the p38 mitogen-activated protein kinases (MAPKs), independent of the Janus kinase (Jak)/signal transducers and activators of transcription (STAT) signaling. In contrast, IL-12 and IL-23 were negatively regulated by the Jak/STAT, phosphatidylinositol 3-kinase (PI3K), and the c-Jun-N-terminal kinase (JNK) MAPKs in IFN-γ-stimulated monocytes. Overall, our results suggest for the first time a differential positive regulation of IL-12p40 and IL-23 by p38 MAPKs independent of the Jak/STAT pathways and negative regulation by the Jak/STAT, JNK, and PI3K pathways in CD14-activated primary human monocytes stimulated with IFN-γ.

Liver stiffness is associated with monocyte activation in HIV-infected Ugandans without viral hepatitis

A high prevalence of liver stiffness, as determined by elevated transient elastography liver stiffness measurement, was previously found in a cohort of HIV-infected Ugandans in the absence of chronic viral hepatitis. Given the role of immune activation and microbial translocation in models of liver disease, a shared immune mechanism was hypothesized in the same cohort without other overt causes of liver disease. This study examined whether HIV-related liver stiffness was associated with markers of immune activation or microbial translocation (MT). A retrospective case-control study of subjects with evidence of liver stiffness as defined by a transient elastography stiffness measurement ≥9.3 kPa (cases=133) and normal controls (n=133) from Rakai, Uganda was performed. Cases were matched to controls by age, gender, HIV, hepatitis B virus (HBV), and highly active antiretroviral therapy (HAART) status. Lipopolysaccharide (LPS), endotoxin IgM antibody, soluble CD14 (sCD14), C-reactive protein (CRP), and D-dimer levels were measured. Conditional logistic regression was used to estimate adjusted matched odds ratios (adjMOR) and 95% confidence intervals. Higher sCD14 levels were associated with a 19% increased odds of liver stiffness (adjMOR=1.19, p=0.002). In HIV-infected individuals, higher sCD14 levels were associated with a 54% increased odds of having liver stiffness (adjMOR=1.54, p<0.001); however, the opposite was observed in HIV-negative individuals (adjMOR=0.57, p=0.001). No other biomarker was significantly associated with liver stiffness, and only one subject was found to have detectable LPS. Liver stiffness in HIV-infected Ugandans is associated with increased sCD14 indicative of monocyte activation in the absence of viral hepatitis or microbial translocation, and suggests that HIV may be directly involved in liver disease.

CD14 and TLR4 mediate cytokine release promoted by electronegative LDL in monocytes

AIMS

Electronegative LDL (LDL(-)), a minor modified LDL present in the circulation, induces cytokine release in monocytes. We aimed to determine the role of the receptor CD14 and toll-like receptors 2 and 4 (TLR2, TLR4) in the inflammatory action promoted by LDL(-) in human monocytes.

METHODS AND RESULTS

Monocytes were preincubated with antibodies to neutralize CD14, TLR2 and TLR4. The release of monocyte chemoattractant protein 1 (MCP1), and interleukin 6 and 10 (IL6 and IL10) promoted by LDL(-) was inhibited 70-80% by antiCD14 and antiTLR4, and 15-25% by antiTLR2. The involvement of CD14 and TLR4 was confirmed by gene silencing experiments. The human monocytic THP1 cell line overexpressing CD14 released more cytokines in response to LDL(-) than the same THP1 cell line without expressing CD14. VIPER, a specific inhibitor of the TLR4 signaling pathway, blocked 75-90% the cytokine release promoted by LDL(-). Cell binding experiments showed that monocytes preincubated with neutralizing antibodies presented lesser LDL(-) binding than non-preincubated monocytes The inhibitory capacity was antiCD14>antiTLR4>>antiTLR2. Cell-free experiments performed in CD14-coated microtiter wells confirmed that CD14 was involved in LDL(-) binding. When LDL(-) and lipopolysaccharide (LPS) were added simultaneously to monocytes, cytokine release was similar to that promoted by LDL(-) alone. Binding experiments showed that LDL(-) and LPS competed for binding to monocytes and to CD14 coated-wells.

CONCLUSIONS

CD14 and TLR4 mediate cytokine release induced by LDL(-) in human monocytes. The cross-competition between LPS and LDL(-) for the same receptors could be a counteracting action of LDL(-) in inflammatory situations.

Markers of microbial translocation and risk of AIDS-related lymphoma

BACKGROUND

Depletion of gut-associated lymphocytes by HIV infection facilitates microbial translocation, which may contribute to non-Hodgkin lymphoma (NHL) risk via chronic immune activation and B-cell hyperstimulation.

METHOD

We therefore examined associations of four microbial translocation markers with subsequent NHL risk in a case-control study nested within four prospective cohort studies of HIV-infected individuals. Prediagnostic blood specimens for 56 NHL cases and 190 controls matched for age, sex, race, specimen type, cohort, and CD4 T-cell count were tested for the endotoxin lipopolysaccharide (LPS), antiendotoxin core antibody (EndoCab), LPS-binding protein (LBP), and soluble CD14 (sCD14).

RESULTS

Elevated levels of sCD14 were associated with significantly increased NHL risk [odds ratio (OR) 2.72 (95% confidence interval [95% CI] 1.29-5.76)]. In subgroup analyses, elevated LPS levels were also associated with significantly increased NHL risk [OR 3.24 (95% CI 1.10-9.53)]. EndoCab and LBP levels were not associated with NHL risk.

CONCLUSION

The association of sCD14 and LPS with NHL risk supports an etiologic role for gut microbial translocation in lymphomagenesis among HIV-infected individuals. Additional studies with larger sample sizes are needed to confirm these observations.

Human cytomegalovirus induces TLR4 signaling components in monocytes altering TIRAP, TRAM and downstream interferon-beta and TNF-alpha expression

Using TLR pathways, primary human cytomegalovirus (HCMV) induces innate responses including the production of inflammatory cytokines. Mounting evidence suggests that LPS recognition by TLR4/MD2/CD14 results in differential utilization of TIRAP-TRAF6 and TRAM-TRIF signaling, thereby leading to transcriptional activation of various cytokine genes. However, relative roles of the TLR4/MD2/CD14 complex and its adaptor proteins TIRAP and TRAM involved in regulating monocyte responses to HCMV are incomplete. Here, we provided evidence supporting the notion that the TLR4/MD2/CD14 complex contributes notably to HCMV-induced signaling and subsequent cytokine production in monocytes. In particular, induction of both IL-6 and IL-8 is associated with elevated TIRAP and reduced TRAM mRNA expression. The latter may serve in a compensatory pathway that yields a robust IFN response when TIRAP signaling is blocked in monocytes incubated with Toledo strain HCMV. Inhibitory studies using antisense oligonucleotides or neutralizing antibodies indicate that IL-6 induction by TLR4/MD2 complex is important for the activation of endogenous CD14 which later acts in concert or synergy with TLR4/MD2 as a factor resulting in IL-8 gene expression. We further show that exogenous recombinant CD14 can potentiate innate immune response via TLR4-dependent and possibly via TLR9-dependent pathways to promote enhanced expression/production of IL-8 and IFN-β, respectively.

Inflammatory mediator release by Brugia malayi from macrophages of susceptible host Mastomys coucha and THP-1 and RAW 264.7 cell lines

OBJECTIVE

To investigate which life stage of the parasite has the ability to stimulate release of pro- or anti-inflammatory mediators from macrophages.

METHODS

The human macrophage/monocyte cell line THP-1, the mouse macrophage cell line RAW 264.7 and naive peritoneal macrophages (PM) from the rodent host Mastomys coucha (M. coucha) were incubated at 37 °C in 5% CO(2) atmosphere with extracts of microfilariae (Mf), third stage infective larvae (L(3)) and adult worms (Ad) of Brugia malayi. After 48 hr post exposure, IL-1β, IL-6, TNF-α, IL-10 and nitric oxide (NO) in cell-free supernatants were estimated.

RESULTS

Extracts of all the life stages of the parasite were capable of stimulating pro- (IL-1β, IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines in both the cell lines and peritoneal macrophages of M. coucha. Mf was the strongest stimulator of pro-inflammatory cytokines followed by L(3) and Ad; however, Ad was a strong stimulator of IL-10 release. Mf was found to have potential to modulate LPS-induced NO release in RAW cells. Ad-induced NO release was concentration dependent with maximum at 20 μg/mL in both RAW and PMs.

CONCLUSIONS

The results show that parasites at all life stages were capable of stimulating pro- (IL-1β, IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines and NO release from macrophages of susceptible host M. coucha, human and mouse macrophage cell lines. Mf can suppress the LPS-induced NO release in RAW cells. The findings also show that the two cell lines may provide a convenient in vitro system for assaying parasite-induced inflammatory mediator release.

Casein α s1 is expressed by human monocytes and upregulates the production of GM-CSF via p38 MAPK

Caseins are major constituents of mammalian milks that are thought to be exclusively expressed in mammary glands and to function primarily as a protein source, as well as to ameliorate intestinal calcium uptake. In addition, proinflammatory and immunomodulatory properties have been reported for bovine caseins. Our aim was to investigate whether human casein α s1 (CSN1S1) is expressed outside the mammary gland and possesses immunomodulatory functions in humans as well. For this purpose, CSN1S1 mRNA was detected in primary human monocytes and CD4(+) and CD8(+) T cells, but not in CD19(+) B cells. CSN1S1 protein was traceable in supernatants of cultured primary human CD14(+) monocytes by ELISA. Similarly, CSN1S1 mRNA and protein were detected in the human monocytic cell lines HL60, U937, and THP1 but not in Mono Mac 6 cells. Moreover, permeabilized human monocytes and HL60 cells could be stained by immunofluorescence, indicating intracellular expression. Recombinant human CSN1S1 was bound to the surface of Mono Mac 6 cells and upregulated the expression of GM-CSF mRNA in primary human monocytes and Mono Mac 6 cells in a time- and concentration-dependent manner. A similar increase in GM-CSF protein was found in the culture supernatants. CSN1S1-dependent upregulation of GM-CSF was specifically blocked by the addition of the p38 MAPK inhibitor ML3403. Our results indicated that human CSN1S1 may possess an immunomodulatory role beyond its nutritional function in milk. It is expressed in human monocytes and stimulates the expression of the proinflammatory cytokine GM-CSF.

Glutathione peroxidase-1 modulates lipopolysaccharide-induced adhesion molecule expression in endothelial cells by altering CD14 expression

CD14 contributes to LPS signaling in leukocytes through formation of toll-like receptor 4/CD14 receptor complexes; however, a specific role for endogenous cell-surface CD14 in endothelial cells is unclear. We have found that suppression of glutathione peroxidase-1 (GPx-1) in human microvascular endothelial cells increases CD14 gene expression compared to untreated or siControl (siCtrl)-treated conditions. Following LPS treatment, GPx-1 deficiency augmented LPS-induced intracellular reactive oxygen species accumulation, CD14 expression, and intercellular adhesion molecule-1 (ICAM-1) mRNA and protein expression compared to LPS-treated control cells. GPx-1 deficiency also transiently augmented LPS-induced vascular cell adhesion molecule-1 (VCAM-1) expression. Adenoviral overexpression of GPx-1 significantly diminished LPS-mediated responses in adhesion molecule expression. Consistent with these findings, LPS responses were also greater in endothelial cells derived from GPx-1-knockout mice, whereas adhesion molecule expression was decreased in cells from GPx-1-overexpressing transgenic mice. Knockdown of CD14 attenuated LPS-mediated up-regulation of ICAM-1 and VCAM-1 mRNA and protein, and it mitigated the effects of GPx-1 deficiency on LPS-induced adhesion molecule expression. Taken together, these data suggest that GPx-1 modulates the endothelial cell response to LPS, in part, by altering CD14-mediated effects.

Varying importance of soluble and membrane CD14 in endothelial detection of lipopolysaccharide

The endothelial response to LPS is critical in the recruitment of leukocytes, thereby allowing the host to survive Gram-negative infection. Herein, we investigated the roles of soluble CD14 (sCD14) and membrane CD14 (mCD14) in the endothelial response to low level LPS (0.1 ng/ml), intermediate level LPS (10 ng/ml), and high level LPS (1000 ng/ml). Removal of sCD14 from serum and sCD14-negative serum prevented low level LPS detection and subsequent response. Addition of recombinant sCD14 back into the endothelial system rescued the endothelial response. GPI-linked mCD14 removal from endothelium or endothelial treatment with a CD14 mAb prevented responses to low-level LPS even in the presence of sCD14. This demonstrates essential nonoverlapping roles for both mCD14 and sCD14 in the detection of low-level LPS. At intermediate levels of LPS, sCD14 was not required, but blocking mCD14 still prevented endothelial LPS detection and E-selectin expression, even in the presence of sCD14, suggesting that sCD14 cannot substitute for mCD14. At very high levels of LPS, the absence of mCD14 and sCD14 did not abrogate TLR4-dependent, E-selectin synthesis in response to LPS. The MyD88 independent pathway was detected in endothelium (presence of TRIF-related adaptor molecule TRAM). The MyD88-independent response (IFN-beta) in endothelium required mCD14 even at the highest LPS dose tested. Our results demonstrate an essential role for endothelial mCD14 that cannot be replaced by sCD14. Furthermore, we have provided evidence for a TRAM pathway in endothelium that is dependent on mCD14 even when other responses are no longer mCD14 dependent.

CD14 mediates cross talk between mononuclear cells and fibroblasts for upregulation of matrix metalloproteinase 9 by Borrelia burgdorferi

Lyme disease is an infection caused by a tick-borne spirochete, Borrelia burgdorferi. Matrix metalloproteinase 9 (MMP-9) was selectively upregulated in the erythema migrans skin lesions of patients with acute Lyme disease. In this study, the mechanism of upregulation of MMP-9 was investigated in vitro and in vivo. The concentrations of MMP-9 and soluble CD14 were markedly elevated in serum from patients with acute Lyme disease and were also upregulated in U937 cells by B. burgdorferi in a time- and concentration-dependent manner. MMP-9 mRNA was expressed at baseline in fibroblasts in the presence or absence of B. burgdorferi. However, when fibroblasts were incubated with supernatants from U937 cells with B. burgdorferi or recombinant CD14, the expression of MMP-9 was significantly increased. This effect was completely abolished by the anti-CD14 antibody. These data suggest that the upregulation of MMP-9 by B. burgdorferi involves the CD14 pathway in infiltrating inflammatory cells. Fibroblasts could be recruited to amplify local production of MMP-9 by acquiring CD14 from macrophages.

Identification of soluble CD14 as an endogenous agonist for Toll-like receptor 2 on human astrocytes by genome-scale functional screening of glial cell derived proteins

Human astrocytes express a limited repertoire of Toll-like receptor (TLR) family members including TLR1-4, which are expressed on the cell surface. Also, TLR3 but not TLR4 activation on astrocytes induces expression of several factors involved in neuroprotection and down-regulation of inflammation rather than in the onset of traditional pro-inflammatory reactions. The notion that astrocyte TLR may thus play a role not only in host defense but also in tissue repair responses prompted us to examine the possibility that endogenous TLR agonists could be expressed in the human central nervous system to regulate the apparently dual astrocyte functions during trauma or inflammation. As a potential source of endogenous agonists, a cDNA library derived from several human brain tumor cell lines was used. Gene pools of this library were transfected into COS-7 cells and the expression products were screened for their ability to induce TLR activation in human primary astrocytes. The screening resulted in the identification of soluble CD14. By using a panel of TLR-transfected HEK293 cells, we found that signaling by soluble CD14 was TLR2 dependent. Moreover, the CD14-triggered TLR2-mediated response in astrocytes lead to the production of CXCL8, IL-6, and IL12p40, whereas typical TLR-induced pro-inflammatory cytokines, like TNF-alpha and IL-1beta, were not produced at detectable levels. In conclusion, our data indicate that apart from its well-known ability to act as a co-receptor for TLR-dependent signaling by peptidoglycans or LPS, soluble CD14 can also act as a direct agonist for TLR2.

CD14 is a ligand for the integrin α4β1

Cell adhesion mediated by the integrin alpha4beta1 plays a key role in many biological processes reflecting both the number and functional significance of alpha4beta1 ligands. The lipopolysaccharide (LPS) receptor, CD14, is a GPI-linked cell surface glycoprotein with a wide range of reported functions and associations, some of which overlap with that of alpha4beta1. This overlap led us to test the specific hypothesis that alpha4beta1 and CD14 interact directly. Jurkat T cells (alpha4beta1(+)) were found to adhere to a recombinant CD14-Fc protein via alpha4beta1, whilst K562 cells (alpha4beta1(-)) did not. However, stable reexpression of the alpha4-subunit conferred this ability. The adhesion of both cell types to CD14 displayed activation state-dependent binding very similar to the interaction of alpha4beta1 with its prototypic ligand, VCAM-1. In solid-phase assays, CD14-Fc bound to affinity-purified alpha4beta1 in a dose-dependent manner that was induced by activating anti-beta1 mAbs. Finally, in related experiments, JY cells (alpha4beta7(+)) were also found to attach to CD14-Fc in an alpha4-dependent manner. In summary, CD14 is a novel ligand for alpha4beta1, exhibiting similar activation-state dependent binding characteristics as other alpha4beta1 ligands. The biological relevance of this interaction will be the subject of further studies.

Soluble CD14 at 2 yr of age: gender-related effects of tobacco smoke exposure, recurrent infections and atopic diseases

The endotoxin receptor soluble CD14 (sCD14) has been implicated in the 'hygiene hypothesis' suggesting reduced allergic sensitization with bacterial stimulation. However, the relationship between early life sCD14 and allergic diseases is conflicting. We aimed to investigate whether possible risk factors for allergic diseases were associated with sCD14 levels at 2 yr of age. In the nested case-control study of the birth cohort studies 'Environment and Childhood Asthma study in Oslo' 411 children selected with recurrent bronchial obstruction (rBO) (n=241) and no bronchial obstruction (n=170) by 2 yr were investigated with skin prick test and structured parental interview at age 2 yr. Exposure to tobacco smoke, pets and infections was recorded semi-annually by questionnaires (0-2 yr). The sCD14 was analysed from frozen, stored serum by ELISA technique. Regression analyses were performed in all subjects with complete data (n=406, 180 girls), and in girls and in boys separately. Mean sCD14 (ng/ml) was significantly higher among girls 2035 (1973-2096) vs. 1947 (1890-2004) (boys). The sCD14 was significantly reduced among girls exposed to antenatal maternal smoking and with parental asthma, after adjusting for age, parental rhino-conjunctivitis, pet keeping and childhood infections. Recurrent otitis media (OM) increased and common colds significantly decreased sCD14 levels in girls. Boys with atopic dermatitis and rBO had reduced sCD14. Pet exposure was not significantly associated with sCD14. We report novel gender-related effects of sCD14 in early life and suggest that gender, tobacco smoke exposure, age and middle ear disease in particular should be accounted for when assessing the role of sCD14 in childhood allergic diseases.

Inflammatory antigens of Brugia malayi and their effect on rodent host Mastomys coucha

The study was aimed at identifying pro- and anti-inflammatory cytokine releasing potential of Brugia malayi adult worm fractions and their role in filarial infection and pathogenesis. THP-1 cells were incubated with soluble somatic Brugia malayi adult worm extract (BmAS) and its Sephadex G-200 fractions BmAFI, BmAFII and BmAFIII and the effect of the fractions on parasitological, immunological and lymph node parameters was assessed in Mastomys coucha. BmAFII stimulated the pro-inflammatory TNF-alpha, IL-1beta and IL-6 release; IL-10 release was insignificant. Sensitization of animals with BmAFII and subsequent intraperitoneal implantation of worms enhanced CMI response. BmAFII also increased lymph node weight and cellularity, stimulated lymph node mast cells and eliminated intraperitoneally instilled worms. BmAFI stimulated several folds more release of IL-10, whereas TNF-alpha release was negligible. Sensitization with BmAFI elicited low CMI responses, moderately stimulated mast cells and facilitated survival of implanted adult parasites. Fifty percent of naive animals exposed to BmAFI showed oedematous lymph nodes and increased node weight. NCP-bound molecules corresponding to BmAFI and II showed cytokine-stimulating potential in vitro. It is concluded that BmAFII is protective and stimulates pro-inflammatory cytokines, whereas BmAFI facilitates parasite survival and stimulates IL-10.

Lack of lipoprotein-dependent effects on the cytotoxic interactions of Actinobacillus actinomycetemcomitans leukotoxin with human neutrophils

A high odds ratio has been reported for hyperlipidemia and periodontal diseases in humans, and the severity of periodontitis seems to correlate with the hyperlipidemic status of the patients. Early studies indicated that the lipoprotein-containing fraction of the serum enhances the leukotoxic activity of the periodontopathogen Actinobacillus actinomycetemcomitans against human polymorphonuclear leukocytes (PMNL). The protease inhibitors of normal serum account for this enhancement, while delipidated serum has no effect on the leukotoxin-dependent PMNL cytolysis. No information exists for the effect of serum lipoproteins or hyperlipidemic serum. The aim of this study was to evaluate the role of serum lipoproteins in the interaction of the leukotoxin of A. actinomycetemcomitans with human PMNL. Purified leukotoxin was mixed with human PMNL prepared from venous blood of healthy subjects and various varying amounts of hyperlipidemic or delipidated serum, or purified serum lipoproteins. The cytolytic activity of leukotoxin was determined by activity of the cytosol enzyme lactate dehydrogenase released from injured PMNL. The degranulating activity of the toxin was measured through the release of the granule components elastase and lactoferrin. Normal human serum without leukotoxin-neutralizing antibodies caused a 4-fold enhancement of the leukotoxic activity when present at concentrations of 5-10% in the reaction mixture. Serum lipoproteins had no effect when added at concentrations that occur normally in serum. At high concentrations, purified low density and very low-density lipoproteins increased the leukotoxicity of the mixture. Nevertheless, hyperlipidemic serum prepared from a normal serum by the addition of autologous lipoproteins had no influence on the leukotoxin-caused cytolysis compared to the normal serum. Pre-incubation of PMNL for 1 h in hyperlipidemic or delipidated serum had no effect on the leukotoxin-induced degranulation of PMNL. The results indicate that the cytotoxic interactions of A. actinomycetemcomitans leukotoxin against human PMNL are not influenced by the presence of serum lipoproteins.

Evidence of a trimolecular complex involving LPS, LPS binding protein and soluble CD14 as an effector of LPS response

The kinetics of the interaction of lipopolysaccharide (LPS), lipopolysaccharide binding protein (LBP) and CD14 was studied using surface plasmon resonance. The association and dissociation rate constants for the binding of LPS and rsCD14 were 2.9 x 10(4) M(-1) s(-1) and 0.07 s(-1) respectively, yielding a binding constant of 4.2 x 10(5) M(-1). Significantly, the presence of LBP increased not only the association rate but also the association constant for the interaction between LPS and CD14 by three orders of magnitude. Our experimental results suggest that LBP interacts with LPS and CD14 to form a stable trimolecular complex that has significant functional implications as it allows monocytes to detect the presence of LPS at a concentration as low as 10 pg/ml or 2 pM, and to respond by secreting interleukin-6. Thus, LBP is not merely transferring LPS to CD14 but it forms an integral part of the LPS-rLBP-rsCD14 complex.

CD14 C(-260)-->T polymorphism, plasma levels of the soluble endotoxin receptor CD14, their association with chronic infections and risk of stable coronary artery disease

OBJECTIVES

We sought to investigate the association of CD14 genotype and plasma levels of soluble (s)CD14 with risk of stable coronary artery disease (CAD), chronic infections and sensitive markers of systemic inflammation.

BACKGROUND

It has been suggested that genetic variation of the CD14 receptor with increased CD14 gene expression might play a role in atherogenesis. A mechanistic link would consist in its contribution to the inflammatory response seen in this disease.

METHODS

We measured levels of sCD14 (microg/ml; ELISA) in 312 patients with angiographically proven CAD and stable angina pectoris, and in 477 age- and gender-matched healthy blood donors. CD14 genotype was determined by polymerase chain reaction. In addition, seropositivity to Chlamydia pneumoniae and Helicobacter pylori, a complete lipid profile and various sensitive systemic markers of inflammation were measured.

RESULTS

CD14 C(-260)-->T genotype was not independently associated with increased risk of CAD after multivariable adjustments (odds ratio [OR] 1.34; 95% confidence interval [CI] 0.84 to 2.16). However, sCD14 plasma levels were higher in subjects with TT genotype compared with those with CT or CC genotype (p = 0.005). Plasma levels were not different between cases and controls (4.2 +/- 1.3 microg/ml vs. 4.3 +/- 1.3 microg/ml, p = NS). In multivariable logistic regression, the OR for the presence of CAD was 1.11 (95% CI, 0.65 to 1.91) if the top quintile of the sCD14 distribution was compared with the bottom quintile. There was no consistent association between seropositivity to either C. pneumoniae or H. pylori, or both, and sCD14 levels and between sCD14 levels or CD14 genotype and the various markers of inflammation.

CONCLUSIONS

These results do not confirm an independent relationship between CD14 genotypes or plasma levels of sCD14 and risk of stable CAD in this population.

B cell stimulating activity of metallothionein in vitro

The effect of metallothionein (MT) on lymphocytes was studied in vitro. Rabbit MT induced the proliferative responses of mouse splenocytes at concentrations of 1-25 microg/ml. MT synergistically enhanced Con A- or LPS-induced proliferative response of splenocytes. A similar effect was also observed for rabbit splenocytes at a similar concentration. Free heavy metals such as Cd and Zn only weakly stimulated splenocytes. 2-mercaptoethanol (2-Me) abrogated the effect of MT, suggesting that thiols in MT play an important role for splenocyte response. MT stimulated splenocytes from MT-knockout mice as well as those from normal control mouse. The responder cells for MT stimulation were B cells and MT also induced B cell differentiation to produce Ig. MT induced the calcium influx of B cells, but not T cells. These results indicate that MT has a potent immunomodulating activity, especially on B cells.