Biomedical subjects

Sergio A Lira

Publications and source records attributed to Sergio A Lira.

At least 19 recordsLinked to original sources

PubMed2007

Monocyte subsets differentially employ CCR2, CCR5, and CX3CR1 to accumulate within atherosclerotic plaques.

Monocytes participate critically in atherosclerosis. There are 2 major subsets expressing different chemokine receptor patterns: CCR2(+)CX3CR1(+)Ly-6C(hi) and CCR2(-)CX3CR1(++)Ly-6C(lo) monocytes. Both C-C motif chemokine receptor 2 (CCR2) and C-X(3)-C motif chemokine receptor 1 (CX3CR1) are linked to progression of atherosclerotic plaques. Here, we analyzed mouse monocyte subsets in apoE-deficient mice and traced their differentiation and chemokine receptor usage as they accumulated within atherosclerotic plaques. Blood monocyte counts were elevated in apoE(-/-) mice and skewed toward an increased frequency of CCR2(+)Ly-6C(hi) monocytes in apoE(-/-) mice fed a high-fat diet. CCR2(+)Ly-6C(hi) monocytes efficiently accumulated in plaques, whereas CCR2(-)Ly-6C(lo) monocytes entered less frequently but were more prone to developing into plaque cells expressing the dendritic cell-associated marker CD11c, indicating that phagocyte heterogeneity in plaques is linked to distinct types of entering monocytes. CCR2(-) monocytes did not rely on CX3CR1 to enter plaques. Instead, they were partially dependent upon CCR5, which they selectively upregulated in apoE(-/-) mice. By comparison, CCR2(+)Ly-6C(hi) monocytes unexpectedly required CX3CR1 in addition to CCR2 and CCR5 to accumulate within plaques. In many other inflammatory settings, these monocytes utilize CCR2, but not CX3CR1, for trafficking. Thus, antagonizing CX3CR1 may be effective therapeutically in ameliorating CCR2(+) monocyte recruitment to plaques without impairing their CCR2-dependent responses to inflammation overall.

Animals↗

PubMed2006

Murine CXCR1 is a functional receptor for GCP-2/CXCL6 and interleukin-8/CXCL8.

Functional interleuin-8 (IL-8) receptors (IL-8RA and IL-8RB: CXCR1 and CXCR2, respectively) have been described in human, monkey, dog, rabbit, and guinea pig. Although three IL-8R homologues have been found in rat, only one of these, rat CXCR2, appears to be functional based on responsiveness to ligands. Similarly, CXC chemokines induce biological responses through the murine homolog of CXCR2, but the identification of functional rodent CXCR1 homologues has remained elusive. We have identified and characterized the mouse CXCR1 homologue (mCXCR1). Murine CXCR1 shares 68 and 88% amino acid identity with its human and rat counterparts, respectively. Similar to the tissue distribution pattern of rat CXCR1, we found murine CXCR1 mRNA expression predominantly in lung, stomach, bone marrow, and leukocyte-rich tissues. In contrast to previous reports, we determined that mCXCR1 is a functional receptor. We show predominant engagement of this receptor by mouse GCP-2/CXCL6, human GCP-2, and IL-8/CXCL8 by binding, stimulation of GTPgammaS exchange, and chemotaxis of mCXCR1-transfected cells. Furthermore, murine CXCR1 is not responsive to the human CXCR2 ligands ENA-78/CXCL5, NAP-2/CXCL7, GRO-alpha, -beta, -gamma/CXCL1-3, or rat CINC-1-3. In addition, we show concomitant elevation of mCXCR1 and its proposed major ligand, GCP-2, positively correlated with paw swelling in murine collagen-induced arthritis. This report represents the first description of a functional CXCR1-like receptor in rodents.

Amino Acid Sequence↗

PubMed2006

A novel model of demyelinating encephalomyelitis induced by monocytes and dendritic cells.

Local inflammation may be a precipitating event in autoimmune processes. In this study, we demonstrate that regulated influx of monocytes and dendritic cells (DC) into the CNS causes an acute neurological syndrome that results in a demyelinating encephalomyelitis. Expansion of monocytes and DC by conditional expression of Flt3 ligand in animals expressing CCL2 in the CNS promoted parenchymal cell infiltration and ascending paralysis in 100% of the mice within 9 days of Flt3 ligand induction. Depletion of circulating monocytes and DC reduced disease incidence and severity. Unlike the classical models of experimental autoimmune encephalomyelitis, depletion of CD4+ and CD8+ T cells did not affect disease induction. T cells and demyelinating lesions were observed in the CNS at a later stage as a result of organ-specific inflammation. We propose that alterations in the numbers or function of monocytes and DC coupled to dysregulated expression of chemokines in the neural tissues, favors development of CNS autoimmune disease.

Acute Disease↗

PubMed2006

The chemokine decoy receptor M3 blocks CC chemokine ligand 2 and CXC chemokine ligand 13 function in vivo.

Chemokines and their receptors play a key role in immune homeostasis regulating leukocyte migration, differentiation, and function. Viruses have acquired and optimized molecules that interact with the chemokine system. These virus-encoded molecules promote cell entry, facilitate dissemination of infected cells, and enable the virus to evade the immune response. One such molecule in the murine gammaherpesvirus 68 genome is the M3 gene, which encodes a secreted 44-kDa protein that binds with high affinity to certain murine and human chemokines and blocks chemokine signaling in vitro. To test the hypothesis that M3 directly interferes with diverse chemokines in vivo, we examined the interaction of M3 with CCL2 and CXCL13 expressed in the pancreas of transgenic mice. CCL2 expression in the pancreas promoted recruitment of monocytes and dendritic cells; CXCL13 promoted recruitment of B and T lymphocytes. Coexpression of M3 in the pancreas blocked cellular recruitment induced by both CCL2 and CXCL13. These results define M3 as multichemokine blocker and demonstrate its use as a powerful tool to analyze chemokine biology.

Animals↗

PubMed2006

The chemokine receptor D6 has opposing effects on allergic inflammation and airway reactivity.

RATIONALE: The D6 chemokine receptor can bind and scavenge several chemokines, including the T-helper 2 (Th2)-associated chemokines CCL17 and CCL22. Although D6 is constitutively expressed in the lung, its pulmonary function is unknown. OBJECTIVES: This study tested whether D6 regulates pulmonary chemokine levels, inflammation, or airway responsiveness during allergen-induced airway disease. METHODS: D6-deficient and genetically matched C57BL/6 mice were sensitized and challenged with ovalbumin. ELISA and flow cytometry were used to measure levels of cytokines and leukocytes, respectively. Mechanical ventilation was used to measure airway reactivity. RESULTS: The ability of D6 to diminish chemokine levels in the lung was chemokine concentration dependent. CCL17 and CCL22 were abundant in the airway, and their levels were attenuated by D6 when they were within a defined concentration range. By contrast, airway concentrations of CCL3, CCL5, and CCL11 were low and unaffected by D6. Allergen-challenged D6-deficient mice had more dendritic cells, T cells, and eosinophils in the lung parenchyma and more eosinophils in the airway than similarly challenged C57BL/6 mice. By contrast, D6-deficient mice had reduced airway responses to methacholine compared with C57BL/6 mice. Thus, D6 has opposing effects on inflammation and airway reactivity. CONCLUSIONS: The ability of D6 to scavenge chemokines in the lung is dependent on chemokine concentration. The absence of D6 increases inflammation, but reduces airway reactivity. These findings suggest that inhibiting D6 function might be a novel means to attenuate airway responses in individuals with allergic asthma.

Allergens↗

PubMed2006

Interaction of mature CD3+CD4+ T cells with dendritic cells triggers the development of tertiary lymphoid structures in the thyroid.

Ectopic expression of CC chemokine ligand 21 (CCL21) in the thyroid leads to development of lymphoid structures that resemble those observed in Hashimoto thyroiditis. Deletion of the inhibitor of differentiation 2 (Id2) gene, essential for generation of CD3-CD4+ lymphoid tissue-inducer (LTi) cells and development of secondary lymphoid organs, did not affect formation of tertiary lymphoid structures. Rather, mature CD3+CD4+ T cells were critical for the development of tertiary lymphoid structures. The initial stages of this process involved interaction of CD3+CD4+ T cells with DCs, the appearance of peripheral-node addressin-positive (PNAd+) vessels, and production of chemokines that recruit lymphocytes and DCs. These findings indicate that the formation of tertiary lymphoid structures does not require Id2-dependent conventional LTis but depends on a program initiated by mature CD3+CD4+ T cells.

Adoptive Transfer↗

PubMed2006

Cutting edge: the silent chemokine receptor D6 is required for generating T cell responses that mediate experimental autoimmune encephalomyelitis.

D6, a promiscuous nonsignaling chemokine binding molecule expressed on the lymphatic endothelium, internalizes and degrades CC chemokines, and D6(-/-) mice demonstrated increased cutaneous inflammation following topical phorbol ester or CFA injection. We report that D6(-/-) mice were unexpectedly resistant to the induction of experimental autoimmune encephalomyelitis due to impaired encephalitogenic responses. Following induction with myelin oligodendroglial glycoprotein (MOG) peptide 35-55 in CFA, D6(-/-) mice showed reduced spinal cord inflammation and demyelination with lower incidence and severity of experimental autoimmune encephalomyelitis attacks as compared with D6(+/+) littermates. In adoptive transfer studies, MOG-primed D6(+/-) T cells equally mediated disease in D6(+/+) or D6(-/-) mice, whereas cells from D6(-/-) mice transferred disease poorly to D6(+/-) recipients. Lymph node cells from MOG-primed D6(-/-) mice showed weak proliferative responses and made reduced IFN-gamma but normal IL-5. CD11c(+) dendritic cells accumulated abnormally in cutaneous immunization sites of D6(-/-) mice. Surprisingly, D6, a "silent" chemokine receptor, supports immune response generation.

Adoptive Transfer↗

PubMed2006

Control of microglial neurotoxicity by the fractalkine receptor.

Microglia, the resident inflammatory cells of the CNS, are the only CNS cells that express the fractalkine receptor (CX3CR1). Using three different in vivo models, we show that CX3CR1 deficiency dysregulates microglial responses, resulting in neurotoxicity. Following peripheral lipopolysaccharide injections, Cx3cr1-/- mice showed cell-autonomous microglial neurotoxicity. In a toxic model of Parkinson disease and a transgenic model of amyotrophic lateral sclerosis, Cx3cr1-/- mice showed more extensive neuronal cell loss than Cx3cr1+ littermate controls. Augmenting CX3CR1 signaling may protect against microglial neurotoxicity, whereas CNS penetration by pharmaceutical CX3CR1 antagonists could increase neuronal vulnerability.

Analysis of Variance↗

PubMed2006

Alloantigen-presenting plasmacytoid dendritic cells mediate tolerance to vascularized grafts.

The induction of alloantigen-specific unresponsiveness remains an elusive goal in organ transplantation. Here we identify plasmacytoid dendritic cells (pDCs) as phagocytic antigen-presenting cells essential for tolerance to vascularized cardiac allografts. Tolerizing pDCs acquired alloantigen in the allograft and then moved through the blood to home to peripheral lymph nodes. In the lymph node, alloantigen-presenting pDCs induced the generation of CCR4+ CD4+ CD25+ Foxp3+ regulatory T cells (Treg cells). Depletion of pDCs or prevention of pDC lymph node homing inhibited peripheral Treg cell development and tolerance induction, whereas adoptive transfer of tolerized pDCs induced Treg cell development and prolonged graft survival. Thus, alloantigen-presenting pDCs home to the lymph nodes in tolerogenic conditions, where they mediate alloantigen-specific Treg cell development and allograft tolerance.

Adoptive Transfer↗

PubMed2006

The human herpesvirus 8 chemokine receptor vGPCR triggers autonomous proliferation of endothelial cells.

We have used a novel conditional transgenic system to study the mechanisms of angioproliferation induced by viral G protein-coupled receptor (vGPCR), the constitutively active chemokine receptor encoded by human herpesvirus 8 (HHV8, also known as Kaposi sarcoma herpesvirus). Using this system, we were able to control temporal expression of vGPCR and to monitor its expression in situ via the use of the surrogate marker LacZ. Upon treatment with doxycycline (DOX), cells expressing vGPCR and LacZ (vGPCR/LacZ(+) cells) progressively accumulated in areas where angioproliferation was observed. Sorted vGPCR/LacZ(+) cells from angiogenic lesions expressed markers characteristic of endothelial progenitor cells, produced angiogenic factors, and proliferated in vitro. Prolonged treatment of transgenic mice with DOX led to development of tumors in the skin of ears, tail, nose, and paws. vGPCR/LacZ(+) cells were frequent in early lesions but scarce within these tumors. Finally, transfer of vGPCR/LacZ(+) cells into Rag1(-/-) mice treated with DOX led to angioproliferation and, with time, to development of tumors containing both vGPCR/LacZ(+) and vGPCR/LacZ(-) cells. Taken together, these results indicate that vGPCR triggers angioproliferation directly and suggest a novel role for this molecule in the pathogenesis of Kaposi sarcoma.

Animals↗

PubMed2006

Neutrophils regulate airway responses in a model of fungal allergic airways disease.

Neutrophils infiltrate airway walls in patients with allergic airway diseases and in animal models of these illnesses, but their contribution to the pathogenesis of airway allergy is not established. We hypothesized that, in a mouse model of airway allergy to the ubiquitous environmental mold, Aspergillus fumigatus, airway neutrophils contribute to disease severity. Ab-mediated neutrophil depletion resulted in reduced airway hyperresponsiveness and remodeling, whereas conditional transgenic overexpression of the neutrophil chemotactic molecule, CXCL1, in airway walls resulted in worsened allergic responses. This worsened phenotype was associated with a marked increase in the number of airway neutrophils but not other lung leukocytes, including eosinophils and lymphocyte subsets, and depletion of neutrophils in sensitized mice with transgenic overexpression of CXCL1 resulted in attenuated airway responses. The number of lung neutrophils correlated with lung matrix metalloproteinase 9 (MMP-9) activity both in the context of neutrophil depletion and with augmented neutrophil recruitment to the airways. Although wild-type and MMP-9-deficient neutrophils homed to the inflamed airways to a similar extent, transfer of wild-type, but not MMP-9-deficient, neutrophils to MMP-9-deficient animals resulted in augmented allergic airway responses. Taken together, these data implicate neutrophils in the pathogenesis of fungal allergic airway disease.

Animals↗

PubMed2006

Dendritic cells rapidly recruited into epithelial tissues via CCR6/CCL20 are responsible for CD8+ T cell crosspriming in vivo.

The nature of dendritic cell(s) (DC[s]) that conditions efficient in vivo priming of CD8+ CTL after immunization via epithelial tissues remains largely unknown. Here, we show that myeloid DCs rapidly recruited by adjuvants into the buccal mucosa or skin are essential for CD8+ T cell crosspriming. Recruitment of circulating DC precursors, including Gr1+ monocytes, precedes the sequential accumulation of CD11c+ MHC class II+ DCs in dermis and epithelium via a CCR6/CCL20-dependent mechanism. Remarkably, a defect in CCR6, local neutralization of CCL20, or depletion of monocytes prevents in vivo priming of CD8+ CTL against an innocuous protein antigen administered with adjuvant. In addition, transfer of CCR6-sufficient Gr1+ monocytes restores CD8+ T cell priming in CCR6( degrees / degrees ) mice via a direct Ag presentation mechanism. Thus, newly recruited DCs likely derived from circulating monocytes are responsible for efficient crosspriming of CD8+ CTL after mucosal or skin immunization.

Adjuvants, Immunologic↗

PubMed2006

CD4+ CD25+ regulatory T-cells inhibit the islet innate immune response and promote islet engraftment.

Early islet cell loss is a significant problem in clinical islet cell transplantation. Diverse stress stimuli induce innate immune responses in islets that contribute to beta-cell dysfunction, inflammation, and loss. Here, we show that cytokine-stimulated murine islets express multiple inflammatory chemokines that recruit T-cells and thereby impair islet function in vitro and in vivo. Both nonislet ductal and exocrine elements and the individual islet cellular components contribute to this innate immune response. CD4+ CD25+ regulatory T-cells inhibit islet chemokine expression through a cell contact-dependent, soluble factor-independent mechanism and inhibit effector T-cell migration to the islet. Regulatory T-cells can also migrate to stimulated islets. Cotransfer of regulatory T-cells with islets in a transplantation model prevents islet innate immune responses and inflammation and preserves normal architecture and engraftment. Regulatory T-cell inhibition of multiple components of innate immune responses may be a fundamental aspect of their function that influences ischemia-reperfusion injury and adaptive immunity.

Animals↗

PubMed2006

Up-regulated expression of the CXCR2 ligand KC/GRO-alpha in atherosclerotic lesions plays a central role in macrophage accumulation and lesion progression.

Macrophage-mediated inflammation is central to atherogenesis. We have determined previously that the CXC chemokine receptor CXCR2 is involved in advanced atherosclerosis. We sought to determine whether one of the ligands of CXCR2, KC/GRO-alpha, can also modulate atherogenesis. KC/GRO-alpha(-/-) mice were generated and mated with the atherosclerosis-prone LDLR(-/-) mice. There was a significant reduction in atherosclerosis in mice lacking KC/GRO-alpha; however, this reduction was only approximately half that seen previously in mice lacking CXCR2 in the leukocyte. To determine whether CXCR2 is involved in the early formation of atherosclerosis, leukocyte-specific CXCR2(-/-) chimeric mice on LDLR(-/-) background were generated. Early fatty streak lesion formation in these mice was not affected by leukocyte CXCR2 deficiency whereas lesions were less developed in mice lacking leukocyte CXCR2 when atherosclerosis was allowed to progress to the intermediate stage. Macrophages were relatively sparse in the lesions of leukocyte CXCR2(-/-) mice despite robust MCP-1 expression. These studies indicate that KC/GRO-alpha/CXCR2 does not play a critical role in recruitment of macrophages into early atherosclerotic lesions but both arterial KC/GRO-alpha and leukocyte-specific CXCR2 expression are central to macrophage accumulation in established fatty streak lesions.

Animals↗

PubMed2005

Absence of CC chemokine receptor 8 enhances innate immunity during septic peritonitis.

An effective clearance of microbes is crucial in host defense during infection. In the present study, we demonstrate that CC chemokine receptor 8 (CCR8) skews innate immune response during septic peritonitis induced by cecal ligation and puncture (CLP). CCR8 was expressed in resident peritoneal macrophages and elicited leukocytes during CLP in the wild-type CCR8+/+ mice. CCR8-/- mice were resistant to CLP-induced lethality relative to CCR8+/+ mice, and this resistance was associated with an augmented bacterial clearance in CCR8-/- mice. In vitro, peritoneal macrophages from CCR8-/- mice, but not neutrophils, exhibited enhanced bactericidal activities relative to those from CCR8+/+ mice. Upon stimulation with the bacterial component LPS, elevated levels of superoxide generation, lysosomal enzyme release, and nitric oxide generation, effector molecules for bacterial killing were detected in CCR8-/- macrophages relative to CCR8+/+ macrophages. In addition, CCR8-/- macrophages produced significantly higher levels than CCR8+/+ macrophages of several cytokines and chemokines known to augment bactericidal activities of leukocytes that include TNF-alpha, IL-12, macrophage-derived chemokine (MDC/CCL22), macrophage inflammatory protein (MIP)-2, and KC. Altogether, these results indicate that CCR8 may have a negative impact on host defense during septic peritonitis, providing a new paradigm for the role of CCR8 in innate immunity.

Animals↗

PubMed2005

Lymph node occupancy is required for the peripheral development of alloantigen-specific Foxp3+ regulatory T cells.

We previously demonstrated that L-selectin (CD62L)-dependent T cell homing to lymph nodes (LN) is required for tolerance induction to alloantigen. To explore the mechanisms of this observation, we analyzed the development and distribution of regulatory T cells (Treg), which play an important protective role against allograft rejection in transplantation tolerance. Alloantigen-specific tolerance was induced using either anti-CD2 plus anti-CD3 mAbs, or anti-CD40L mAbs plus donor-specific transfusion, in fully mismatched (BALB/c donor, C57BL/6 recipient) vascularized cardiac allografts. An expansion of CD4(+)CD25(+)CD62L(high) T cells was observed specifically within the LN of tolerant animals, but not in other anatomic sites or under nontolerizing conditions. These cells exhibited a substantial up-regulation of Foxp3 expression as measured by real-time PCR and by fluorescent immunohistochemistry, and possessed alloantigen-specific suppressor activity. Neither LN nor other lymphoid cells expressed the regulatory phenotype if recipients were treated with anti-CD62L mAbs, which both prevented LN homing and caused early allograft rejection. However, administration of FTY720, a sphingosine 1-phosphate receptor modulator that induces CD62L-independent T cell accumulation in the LNs, restored CD4(+)CD25(+) Treg in the LNs along with graft survival. These data suggest that alloantigen-specific Foxp3(+)CD4(+)CD25(+) Treg develop and are required within the LNs during tolerization, and provide compelling evidence that distinct lymphoid compartments play critical roles in transplantation tolerance.

Animals↗

PubMed2005

The human herpes virus 8-encoded chemokine receptor is required for angioproliferation in a murine model of Kaposi's sarcoma.

Kaposi's sarcoma (KS)-associated herpesvirus or human herpes virus 8 is considered the etiological agent of KS, a highly vascularized neoplasm that is the most common tumor affecting HIV/AIDS patients. The KS-associated herpesvirus/human herpes virus 8 open reading frame 74 encodes a constitutively active G protein-coupled receptor known as vGPCR that binds CXC chemokines with high affinity. In this study, we show that conditional transgenic expression of vGPCR by cells of endothelial origin triggers an angiogenic program in vivo, leading to development of an angioproliferative disease that resembles KS. This angiogenic program consists partly in the expression of the angiogenic factors placental growth factor, platelet-derived growth factor B, and inducible NO synthase by the vGPCR-expressing cells. Finally, we show that continued vGPCR expression is essential for progression of the KS-like phenotype and that down-regulation of vGPCR expression results in reduced expression of angiogenic factors and regression of the lesions. Together, these findings implicate vGPCR as a key element in KS pathogenesis and suggest that strategies to block its function may represent a novel approach for the treatment of KS.

Animals↗

PubMed2005

The chemokine receptor D6 limits the inflammatory response in vivo.

How the inflammatory response is initiated has been well defined but relatively little is known about how such responses are resolved. Here we show that the D6 chemokine receptor is involved in the post-inflammatory clearance of beta-chemokines from cutaneous sites. After induction of inflammation by phorbol esters, wild-type mice showed a transient inflammatory response. However, in D6-deficient mice, an excess concentration of residual chemokines caused a notable inflammatory pathology with similarities to human psoriasis. These results suggest that D6 is involved in the resolution of the cutaneous inflammatory response.

Animals↗