Fcα Receptor Type I and Its Association with Atherosclerosis Development.

Objectives: Atherosclerosis is a chronic inflammatory disease characterized by lipid accumulation and local inflammation, which are regulated by the immune system. The immunological aspects of this disease are unclear. Immunoglobulin A regulates many cell responses through interactions with Fcα receptor type I (FcαRI). Anti-FcαRI antibody inhibits activating receptors by inducing an inhibitory immunoreceptor tyrosine-based activation motif configuration. However, the role of FcαRI in atherosclerosis development is unclear. Here, we investigated the utility of FcαRI targeting to induce inhibitory immunoreceptor tyrosine-based activation motif signaling in atherosclerosis treatment. Materials: ApoE-/- transgenic mice expressing the FcαRIR209L/FcRγ chimeric protein (FcαRIR209L/FcRγApoE-/- mice) were generated. We prepared an FcαRIR209L/FcRγ transfectant (I3D) from a mouse macrophage cell line (RAW264.7). Methods: Anti-FcαRI or control antibody was used to investigate a high-fat-diet-induced FcαRIR209L/FcRγApoE-/- mouse model of atherosclerosis. The antibody was also used to assess macrophage foam cell formation via Oil Red O staining and mitogen-activated protein kinase signaling via immunoblotting in the FcαRIR209L/FcRγ-expressing RAW264.7 macrophage cell line I3D. Results: Targeting of monovalent FcαRI induced inhibitory effects in the FcαRIR209L/FcRγApoE-/- mouse model of atherosclerosis by inhibiting macrophage infiltration. FcαRI targeting using the anti-FcαRI antibody also reduced mitogen-activated protein kinase signaling and foam cell formation, leading to decreased interleukin (IL)-1b and monocyte chemoattractant protein (MCP)-1. Conclusions: We demonstrated that targeting monovalent FcαRI suppresses atherosclerosis development. These findings can support the future clinical exploration of FcαRI targeting for atherosclerosis treatment.

Reversal of Arthritis by Human Monomeric IgA Through the Receptor-Mediated SH2 Domain-Containing Phosphatase 1 Inhibitory Pathway.

OBJECTIVE: Rheumatoid arthritis (RA), one of the most frequent chronic inflammatory rheumatic disorders, is characterized by the presence of autoantibodies and joint infiltration by activated immune cells, leading to cartilage and bone destruction. IgA occurs predominantly as monomers (mIgA) in plasma and regulates many cell responses through interaction with the Fcα receptor type I (FcαRI). FcαRI targeting by anti-FcαRI Fab inhibits activating receptors by inducing an inhibitory immunoreceptor tyrosine-based activation motif (ITAMi) configuration through SH2 domain-containing phosphatase 1 (SHP-1) recruitment. The aim of this study was to investigate the potential utility of mIgA for the treatment of arthritis by acting as an inducer of ITAMi signaling. METHODS: The effect of plasma-derived human mIgA on inhibition of multiple heterologous receptors was evaluated on FcαRI+ cell transfectants, blood phagocytes from healthy individuals, and synovial cells from RA patients. FcαRI-transgenic mice and wild-type mice treated with mIgA were studied in models of collagen antibody-induced arthritis (CAIA) and collagen-induced arthritis (CIA). The mice were assessed for development of arthritis using an arthritis score, and joint tissue samples were evaluated for the extent of leukocyte infiltration and expression of phosphatase. RESULTS: Treatment with mIgA impaired cell activation in an FcαRI-FcRγ-dependent manner, involving ITAMi signaling. Human mIgA or anti-FcαRI Fab were strongly effective in either preventing or attenuating CAIA or CIA in FcαRI-transgenic mice. Administration of mIgA markedly inhibited the recruitment of leukocytes to the inflamed joints of mice, which was associated with induction of SHP-1 phosphorylation in joint tissue cells. Moreover, mIgA reversed the state of inflammation in the synovial fluid of RA patients by inducing an ITAMi configuration. CONCLUSION: These results demonstrate a therapeutic potential of human mIgA in experimental arthritis. The findings support future clinical exploration of mIgA for the treatment of RA.

Inhibitory ITAM signaling traps activating receptors with the phosphatase SHP-1 to form polarized "inhibisome" clusters.

The ability of immunoreceptor tyrosine-based activation motif (ITAM)-bearing receptors to inhibit, rather than activate, signaling by other receptors is a regulatory mechanism of immune homeostasis. However, it remains unclear how inhibitory ITAM (ITAMi) receptor signaling and Src homology 2 (SH2) domain-containing phosphatase-1 (SHP-1), which is recruited to ITAMs, target multiple heterologous activating responses without coaggregating with the associated activating receptors. We found that ITAMi signaling triggered by the binding of monomeric ligands to the type I immunoglobulin A (IgA) Fc receptor (FcαRI) induced its dynamic cosegregation with heterologous activating receptors, signaling effectors, and the inhibitory phosphatase SHP-1 into polarized intracellular clusters that we call "inhibisomes." Formation of inhibisomes was preceded by the recruitment of FcαRI and SHP-1 into lipid rafts. Cosegregation required the depolymerization of actin, which depended on SHP-1, and inhibisome formation was abolished by knockdown of SHP-1 and by actin-depolymerizing drugs. Thus, SHP-1- and actin depolymerization-dependent spatiotemporal compartmentalization of ITAMi-containing receptors into lipid rafts, regions associated with intracellular signaling, represents a key event in the integration of ITAMi-mediated inhibitory signals.

Improvement of rapidly progressive lupus nephritis associated MPO-ANCA with tacrolimus.

A 43-year-old Japanese woman with systemic lupus erythematosus (SLE) developed rapidly progressive renal failure and nephritic syndrome with a high titer of myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA). Methylprednisolone pulse therapy did not suppress the progression of renal failure. Intravenous cyclophosphamide pulse therapy and administration of azathioprine was abandoned due to adverse effects. Tacrolimus was employed as an alternative immunosuppressive therapy and was well tolerated, effectively preventing renal failure. Oral prednisolone dosage was successfully tapered without recurrence, along with decreasing titer of MPO-ANCA. Renal biopsy showed diffuse proliferative lupus nephritis (International Society of Nephrology/Renal Pathology Society class IV-G A/C) with crescent formation. These findings indicate that in addition to lupus nephritis, which usually results from deposition of circulating or locally formed immune complexes, MPO-ANCA may be involved in the pathogenesis of crescentic glomerulonephritis. Furthermore, we propose that tacrolimus is an effective immunosuppressant for MPO-ANCA-related renal crisis in diffuse proliferative lupus nephritis.

Inhibitory ITAM signaling by Fc alpha RI-FcR gamma chain controls multiple activating responses and prevents renal inflammation.

Inhibitory signaling is an emerging function of ITAM-bearing immunoreceptors in the maintenance of homeostasis. Monovalent targeting of the IgA Fc receptor (FcalphaRI or CD89) by anti-FcalphaRI Fab triggers potent inhibitory ITAM (ITAM(i)) signaling through the associated FcRgamma chain (FcalphaRI-FcRgamma ITAM(i)) that prevents IgG phagocytosis and IgE-mediated asthma. It is not known whether FcalphaRI-FcRgamma ITAM(i) signaling controls receptors that do not function through an ITAM and whether this inhibition requires Src homology protein 1 phosphatase. We show in this study that FcalphaRI-Fcgamma ITAM(i) signals depend on Src homology protein 1 phosphatase to target multiple non-ITAM-bearing receptors such as chemotactic receptors, cytokine receptors, and TLRs. We found that anti-FcalphaRI Fab treatment in vivo reduced kidney inflammation in models of immune-mediated glomerulonephritis and nonimmune obstructive nephropathy by a mechanism that involved decreased inflammatory cell infiltration and fibrosis development. This treatment also prevented ex vivo LPS activation of monocytes from patients with lupus nephritis or vasculitis, as well as receptor activation through serum IgA complexes from IgA nephropathy patients. These findings point to a crucial role of FcalphaRI-FcRgamma ITAM(i) signaling in the control of multiple heterologous or autologous inflammatory responses. They also identify anti-FcalphaRI Fab as a new potential therapeutic tool for preventing progression of renal inflammatory diseases.

Mast cells and inflammatory kidney disease.

Inflammatory kidney disease involves a complex network of interactions between resident kidney and infiltrating hematopoietic cells. Mast cells (MCs) are constitutively found in kidneys in small numbers but increase considerably in various renal diseases. While this increase is usually interpreted as a sign of pathological involvement, recent data using MC-deficient animals show their ability to restore kidney homeostasis. In anti-glomerular basement membrane antibody-induced glomerulonephritis, MCs are protective by initiating repair and remodeling functions counteracting the devastating effects of glomerular injury. Protection may also include immunoregulatory capacities to limit autoreactive T-cell responses. MCs also control tubulointerstitial fibrosis by activating tissue remodeling and neutralizing fibrotic factors. Release of mediators by MCs during inflammation, however, could also promote unwanted responses that ultimately lead to destruction of kidney structure, as exemplified by data showing either protection or aggravation in related renal disease models. Similarly, while the action of proteases may initially be beneficial, the generation of fibrosis-promoting angiotensin II by chymase also shows the limits of adaptive responses to achieve homeostasis. Thus, it is likely the physiological context involving the interaction with other cells and inflammatory mediators that determines the final action of MCs in the development of kidney disease.

IgA Fc receptor I is a molecular switch that determines IgA activating or inhibitory functions.

IgA Fc receptor I, FcalphaRI or CD89, an ITAM-bearing receptor, has revealed unique genetic, structure and function features among immunoreceptors. While all genes encoding for the human Fc receptors are located in chromosome 1, the FcalphaRI gene has been found in a cluster in 19q13 that includes the killer inhibitory receptors (KIRs) and the leukocyteimmunoglobulin- like receptors (LIRs). FcalphaRI-IgA complexes display an original crystal structure and a 2:1 stoichiometry. Our results show that intrinsic signals elicited by FcalphaRI have outlined the particularity of this receptor, since it could function in two opposite ways: cell activation and inhibition of a heterologous FcR. Contrary to the dogma that receptor multimerization is necessary to ensure signaling, we demonstrated that monomeric targeting of FcalphaRI is sufficient to trigger a low-intensity signaling cascade that leads to cell desensitization by recruiting the tyrosine phosphatase SHP-1. By contrast, multimerization of FcalphaRI allows a high-intensity signaling pathway that leads to the recruitment of tyrosine kinase Syk and cell activation. Both types of signals require the FcRgamma-ITAM motif. This dual function is unique among ITAM-bearing FcR and led us to postulate that ITAM motifs could deliver an unexpected array of signaling intensity. These findings redefine FcalphaRI as a molecular switch of the immune system that mediates both pro- and anti-inflammatory functions of IgA.

Fc alpha receptor I activation induces leukocyte recruitment and promotes aggravation of glomerulonephritis through the FcR gamma adaptor.

Myeloid cells bear Fc receptors (FcR) that mediate inflammatory signaling through the ITAM-containing FcRgamma adaptor. They express FcRgamma-associated FcalphaRI, which modulate either activating or inhibitory signaling depending on the type of ligand interaction. The role of FcalphaRIgamma in disease progression remains unknown, notably in IgA nephropathy (IgAN), one of major causes of end-stage renal disease, in which large amounts of circulating IgA-immune complexes (IC) may mediate receptor activation. To analyze the involvement of FcalphaRI activation in glomerulonephritis (GN), we generated Tg mice expressing a mutated, signaling-incompetent, human FcalphaRI(R209L) that cannot associate with FcRgamma. Like FcalphaRI(wt)-Tg mice, they developed mesangial IgA deposits but not macrophage infiltration. FcalphaRI activation in FcalphaRI(wt), but not in FcalphaRI(R209L), Tg mice resulted in marked inflammation with severe proteinuria and leukocyte infiltration in spontaneous IgAN or anti-glomerular basement membrane Ab-induced GN models. Receptor triggering of syngenically transferred FcalphaRI(wt) Tg macrophages into non-Tg animals induced their recruitment into injured kidneys during GN development. FcalphaRI(wt) cross-linking on macrophages activated MAP kinases and production of TNF-alpha and MCP-1. Moreover, IgA-IC from IgAN patients activated FcalphaRI and induced TNF-alpha production. Thus, FcalphaRI activation mediates GN progression by initiating a cytokine/chemokine cascade that promotes leukocyte recruitment and kidney damage.

IgA Fc receptor I signals apoptosis through the FcRgamma ITAM and affects tumor growth.

The IgA Fc receptor (FcalphaRI) has dual proinflammatory and anti-inflammatory functions that are transmitted through the immunoreceptor tyrosine-based activation motifs (ITAMs) of the associated FcRgamma subunit. Whereas the involvement of FcalphaRI in inflammation is well documented, little is known of its anti-inflammatory mechanisms. Here we show that monomeric targeting of FcalphaRI by anti-FcalphaRI Fab or serum IgA triggers apoptosis in human monocytes, monocytic cell lines, and FcalphaRI+ transfectants. However, the physiologic ligand IgA induced apoptosis only when cells were cultured in low serum conditions, indicating differences with induction of anti-inflammatory signaling. Apoptosis signaling required the FcRgamma ITAM, as cells transfected with FcalphaRI or with a chimeric FcalphaRI-FcRgamma responded to death-activating signals, whereas cells expressing a mutated FcalphaRI(R209L) unable to associate with FcRgamma, or an ITAM-mutated chimeric FcalphaRI-FcRgamma, did not respond. FcalphaRI-mediated apoptosis signals were blocked by treatment with the pan-caspase inhibitor zVAD-fmk, involved proteolysis of procaspase-3, and correlated negatively with SHP-1 concentration. Anti-FcalphaRI Fab treatment of nude mice injected subcutaneously with FcalphaRI+ mast-cell transfectants prevented tumor development and halted the growth of established tumors. These findings demonstrate that, on monomeric targeting, FcalphaRI functions as an FcRgamma ITAM-dependent apoptotic module that may be fundamental for controlling inflammation and tumor growth.

Mast cell-mediated remodeling and fibrinolytic activity protect against fatal glomerulonephritis.

Mast cells are detrimental in several inflammatory diseases; however, their physiological roles are also increasingly recognized. Recent data suggest that mast cells may also be involved in renal diseases. We therefore used congenitally mast cell-deficient W/W(v) mice and normal +/+ littermates to assess their role in anti-glomerular basement membrane-induced glomerulonephritis. Following administration of anti-glomerular basement membrane Abs, W/W(v) mice exhibited increased mortality as compared with +/+ mice owing to rapid deterioration of renal function. Reconstitution of the mast cell population in W/W(v) mice restored protection. This was independent of activating FcgammaR, as protection was also obtained using mast cells deficient in FcRgamma. Comparative histological analysis of kidneys showed that deterioration of renal function was caused by the presence of thick layers of subendothelial glomerular deposits in W/W(v) mice, while +/+ mice or mast cell-reconstituted W/W(v) mice showed significantly less. Deposits appeared during the early phase of disease and persisted thereafter, and were accompanied by enhanced macrophage recruitment. Immunohistochemical analysis revealed increased amounts of fibrin and type I collagen in W/W(v) mice, which were also unable to maintain high tissue plasminogen activator and urinary-type plasminogen activator activity in urine in the heterologous phase of disease. Our results indicate that mast cells by their ability to mediate remodeling and repair functions are protective in immune complex-mediated glomerulonephritis.

B lymphocytes undergo apoptosis because of FcgammaRIIb stress response to infection: a novel mechanism of cell death in sepsis.

Sepsis is predominantly characterized by proinflammatory signs in its initial phase, but can be also associated with immune suppression that can be a consequence of apoptotic cell death. The role of Fc receptors (FcRs) is poorly understood in this disease, and it was recently shown that, in addition to the promotion of opposite inflammatory responses, they are implicated in apoptosis. Using a model of peritonitis in mice that do not express activating FcRs, we tested the hypothesis that FcgammaRIIb, the only known immunoglobulin G receptor capable of inducing apoptosis, would participate in the induction of this kind of cell death during serious infection. The blocking of this receptor by a monoclonal antibody significantly decreased the number of apoptotic splenic B cells, demonstrating its involvement in apoptosis. FcgammaRIIb-mediated apoptosis was neither the result of increased TNFalpha levels nor was it associated with IL-10 production. Finally, the decreased apoptosis after mice treatment with FcgammaRIIb-blocking antibody was not sufficient to increase its survival. Thus, we conclude that although apoptosis is a multifactorial phenomenon in sepsis, one of these factors is the inhibitory immunoglobulin G receptor FcgammaRIIb. FcgammaRIIb stress response to infection is a novel mechanism that contributes to the comprehension of apoptosis in sepsis.

FcgammaRIIa-131R allele and FcgammaRIIIa-176V/V genotype are risk factors for progression of IgA nephropathy.

BACKGROUND: Fcgamma receptors (FcgammaRs) may play an important role in positive and negative regulation of immune cell responses and immune complex (IC) clearance. Mesangial IgG deposition and circulating IgG/IgA-IC in sera are observed in patients with IgA nephropathy (IgAN). Therefore, the pathological roles of IgG-IC in IgAN have been discussed. On the other hand, several studies have identified FcgammaR polymorphisms (FcgammaRIIa, FcgammaRIIIa and FcgammaRIIIb) that determine susceptibility to autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. The objective of the present study was to clarify whether FcgammaR polymorphisms influence susceptibility to IgAN, clinical features or severity in patients with IgAN. METHODS: Japanese patients with IgAN (n = 124) and healthy controls (n = 100) were genotyped for FcgammaR polymorphisms (FcgammaRIIa-131H or R, FcgammaRIIIa-176F or V and FcgammaRIIIb-NA1 or -NA2). The genotyping of these polymorphisms was performed using allele-specific polymerase chain reaction (PCR) methods. Associations among FcgammaR polymorphisms and susceptibility, age of onset, levels of serum immunoglobulins, intensity of glomerular IgG deposition and pathological severity were analysed. RESULTS: These three FcgammaR polymorphisms showed no significant differences in genotype and allele frequencies between the IgAN patients and healthy controls. Each FcgammaR polymorphism had no influence on age of onset, serum levels of IgG and glomerular IgG deposition in IgAN. However, FcgammaRIIa-131R (R/R or H/R) or FcgammaRIIIa-176V homozygous carriers (V/V) showed significantly more severe injury than FcgammaRIIa-131H homozygous (H/H) (P < 0.03) or FcgammaRIIIa-176F carriers (F/F or F/V) (P < 0.03), respectively. CONCLUSION: The present study shows that polymorphisms of FcgammaRIIa and FcgammaRIIIa influence the severity of IgAN in Japanese patients but not the incidence, suggesting that IgG-IC may play important roles in the progression and prognosis of this disease via FcgammaRs.

Suppression of serum IgE response and systemic anaphylaxis in a food allergy model by orally administered high-dose TGF-beta.

Some epidemiological or association studies suggest that transforming growth factor-beta (TGF-beta) in breast milk may be a decisive factor in diminishing the risk of allergic diseases during infancy. The observations have prompted us to investigate whether TGF-beta, when taken orally, can affect allergic immune responses. Repeated high-dose ovalbumin peptide (OVA) feeding was previously reported to induce OVA-specific IgE production and an anaphylactic reaction after intravenous challenge of OVA in OVA-TCR transgenic mice, which might represent a model for food allergy. By using this model, we showed here that oral administration of high-dose TGF-beta simultaneously with OVA feeding significantly inhibited the OVA-specific IgE elevation and anaphylactic reaction in OVA-TCR transgenic DO11.10 mice. These effects were associated with suppression of OVA-specific IL-4 production and GATA-3 expression and with up-regulation of IFN-gamma production and T-bet expression by splenocytes. Intra-peritoneal injection of anti-TGF-beta-neutralizing antibody abolished the inhibitory effects of orally administered TGF-beta on the serum IgE response and anaphylactic reaction after OVA feeding in DO11.10 mice. Interestingly, oral administration of high-dose TGF-beta suppressed activation-induced T cell death induced by OVA feeding in DO11.10 mice. We thus conclude that TGF-beta, when taken orally at high dose, has the capacity to modulate a food allergy-related reaction, at least in part, through its systemic activity.

Smad3 deficiency in mast cells provides efficient host protection against acute septic peritonitis.

Mast cells play an important role in innate immunity as well as in allergic reaction. However, regulatory mechanisms underlying mast cell-mediated innate immune responses remain largely unknown. Here we determined whether Smad3, a major signal transducer of TGF-beta, regulates innate immune response by mast cells against Gram-negative bacteria. Bone marrow-derived mast cells (BMMC) obtained from Smad3 null mutant mice showed augmented capacity to produce proinflammatory cytokines upon stimulation with a Gram-negative bacteria-associated product, LPS. In acute septic peritonitis model induced by cecal ligation and puncture, mast cell-deficient W/W(v) mice reconstituted with Smad3 null BMMC had significantly higher survival rate than W/W(v) mice reconstituted with wild-type BMMC, which was associated with higher production of proinflammatory cytokines in the peritoneal cavity. These in vitro and in vivo results suggest that Smad3 in mast cells functions as inhibitory for mast cell-mediated innate immune response against Gram-negative bacteria. Suppression of Smad3 expression in mast cells may thus have therapeutic potential for Gram-negative bacterial infection such as acute septic peritonitis by augmenting innate immune responses of mast cells.

Identification of FcalphaRI as an inhibitory receptor that controls inflammation: dual role of FcRgamma ITAM.

Serum IgA is considered a discrete housekeeper of the immune system with multiple anti-inflammatory functions, whereas IgA-immune complexes mediate inflammatory responses. Here, we identify FcalphaRI as a molecular device that determines the nature of IgA responses. In the absence of sustained aggregation, receptor targeting by serum IgA or anti-FcalphaRI Fab inhibits activating responses of heterologous FcgammaR or FcepsilonRI. The inhibitory mechanism involves recruitment of tyrosine phosphatase SHP-1 to FcalphaRI and impairment of Syk, LAT, and ERK phosphorylation induced by FcepsilonRI engagement. SHP-1 recruitment is dependent on ERK. Conversely, sustained aggregation of FcalphaRI by multimeric ligands stimulates cell activation by recruiting high amounts of Syk and aborting SHP-1 binding. Both types of signals require the FcRgamma-ITAM motif. Anti-FcalphaRI Fab treatment suppresses manifestations of allergic asthma in FcalphaRI transgenic mice. These findings redefine FcalphaRI as a bifunctional inhibitory/activating receptor of the immune system that mediates both anti- and proinflammatory functions of IgA.

Smad3 deficiency attenuates renal fibrosis, inflammation,and apoptosis after unilateral ureteral obstruction.

BACKGROUND: Transforming growth factor-beta (TGF-beta) has been implicated in the development of renal fibrosis induced by unilateral ureteral obstruction (UUO). However, there is little information on signaling pathways mediating TGF-beta activity involved in molecular and cellular events leading to renal fibrosis induced by UUO. In this study, we sought to determine whether Smad3, a major signaling component of TGF-beta, mediated renal fibrosis induced by UUO. METHODS: Renal fibrosis, inflammation, and apoptosis induced by UUO were macroscopically and histologically compared between wild-type mice and Smad3 null mice. RESULTS: Gross appearance of the kidney after UUO showed relatively intact kidney in Smad3 null mice [Smad3(-/-) mice] when compared with that of wild-type mice [Smad3(+/+) mice]. Renal interstitial fibrosis based on the interstitial area stained with Aniline-blue or Sirius red solution was significantly attenuated in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Deposition of type I and type III collagens were also significantly reduced in the obstructed kidney of Smad3(-/-) mice. In addition, the numbers of myofibroblasts, macrophages, and CD4/CD8 T cells infiltrated into the kidney after UUO were significantly attenuated in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Furthermore, terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) staining after UUO showed significantly reduced number of tubular apoptotic cells in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Endogenous Smad pathway was activated in the obstructed kidney after UUO in wild-type mice as judged by the increase of phosphorylated Smad2 or phosphorylated Smad2/3-positive cells in renal interstitial area. CONCLUSION: Smad3 deficiency attenuated renal fibrosis, inflammation, and apoptosis after UUO, suggesting that Smad3 was a key molecule mediating TGF-beta activity leading to real fibrosis after UUO.

Involvement of p300 in TGF-beta/Smad-pathway-mediated alpha2(I) collagen expression in mouse mesangial cells.

BACKGROUND: Transforming growth factor beta 1 (TGF-beta1) induces alpha2(I) collagen gene (COL1A2) expression in mesangial cells through physical and functional cooperation of Smad proteins and Sp1. A transcriptional coactivator, p300, is also suggested to play an important role in TGF-beta1/Smad signal transduction. However, the role of p300 in TGF-beta1/Smad-pathway-mediated transcriptional activation of the COL1A2 gene in mesangial cells is still obscure. METHODS: Endogenous p300 expression and its modulation by TGF-beta1 were evaluated by Western blotting and immunofluorescence. The physical interaction of p300 with Smad2/3 was examined by immunoprecipitation followed by Western blotting. The functional role of p300 in TGF-beta1/Smad-pathway-mediated COL1A2 transcription was investigated in cotransfection experiments using a COL1A2 promoter-luciferase reporter gene construct and p300 expression plasmids. RESULTS: TGF-beta1 induced COL1A2 gene expression in cultured mouse mesangial cells which was blocked by overexpression of inhibitory Smad7. In addition, TGF-beta1-induced nuclear export of endogenous Smad7 was observed in mouse mesangial cells. Endogenous p300 was expressed in the nucleus of the cells. TGF-beta1 induced interaction of endogenous p300 with Smad2/3, and a dominant negative construct of p300 inhibited the TGF-beta1-induced COL1A2 expression in cultured mouse mesangial cells. CONCLUSIONS: p300 may be involved in TGF-beta1/Smad-pathway-mediated type I collagen gene transcription in mouse mesangial cells. Our findings would reveal a molecular basis of TGF-beta1-induced type I collagen gene transcription in mouse mesangial cells.

Chronic graft-versus-host autoimmune disease in Fc receptor gamma chain-deficient mice results in lipoprotein glomerulopathy.

Lipoprotein glomerulopathy (LPG) is a unique renal disease characterized by intraglomerular lipoprotein thrombi associated with severe proteinuria and frequent progression to renal failure. The histologic hallmark of LPG is the presence of laminated thrombi, consisting of lipid droplet, within the lumina of dilated glomerular capillaries. The findings of thrombi consisting of lipoproteins raised the possibilities that LPG might be related to a primary abnormality in lipid metabolism. However, the precise pathogenic basis of LPG remains unresolved. It was herein found that chronic graft-versus-host disease (GVHD) induced by the transfer of Ia-incompatible spleen cells from B6.C-H2(bm12) into coisogenic C57BL/6 mice with deficiency of Fc receptor gamma chain (FcRgamma) resulted in glomerulopathy that resembled LPG. The uptake of acetylated LDL was partially decreased in peritoneal macrophages isolated from FcRgamma-deficient mice compared with wild-type mice, suggesting that partial impairment of modified LDL uptake might contribute to the development of LPG associated with chronic GVHD in FcRgamma-deficient mice. LPG has been suggested to be a disorder of primary abnormality in lipid metabolism; these findings would therefore provide novel insight into the disease process.

Localization of intestinal intraepithelial T lymphocytes involves regulation of alphaEbeta7 expression by transforming growth factor-beta.

Induction of alphaEbeta7 expression on T cells by transforming growth factor (TGF)-beta is thought to be important for intestinal intraepithelial T lymphocyte (IEL) entry into the epithelial compartment. However, there has been no in vivo evidence that up-regulation of alphaEbeta7 expression on T cells by TGF-beta is critical for the selective localization of intestinal IEL in the epithelial area. We have recently established transgenic mice expressing Smad7 under the control of a distal lck promoter where TGF-beta/Smad signaling is specifically blocked in mature T cells. Here we showed that TGF-beta-mediated up-regulation of alphaEbeta7 was impaired on T cells isolated from the Smad7 transgenic mice associated with reduced numbers of intestinal IEL when compared with that in wild-type littermates. These results indicated that failure to induce alphaEbeta7 on T cells by TGF-beta resulted in reduced numbers of intestinal IEL, suggesting the importance of alphaEbeta7 expression by TGF-beta in selective localization of intestinal IEL.

Selective accumulation of CCR4+ T lymphocytes into renal tissue of patients with lupus nephritis.

OBJECTIVE: Some chemokine receptors, such as CCR5 and CCR4, are differentially expressed on Th1 and Th2 cells. To determine whether differential expression of the chemokine receptors occurs in patients with lupus nephritis, we examined the expression of CCR4 and CCR5 on peripheral blood lymphocytes and mononuclear cells infiltrated into the renal tissue of patients with lupus nephritis. METHODS: The expression of CCR4 and CCR5 on CD4+,CD45RO+ cells was analyzed by flow cytometry and compared between patients with systemic lupus erythematosus (SLE) and healthy controls. Correlation between the absolute number of CCR4+ or CCR5+ cells and clinical parameters was also analyzed. Mononuclear infiltrates in the renal tissue of SLE patients were analyzed for the expression of CCR4, CCR5, and CD4 by immunohistochemical staining. RESULTS: The absolute number of CCR4+, but not CCR5+, T lymphocytes in the peripheral blood was significantly decreased in the patients with SLE compared with that in the healthy controls, and this positively correlated with the serum levels of C3 and CH50. Most of the CD4+ T lymphocytes that infiltrated into the renal tissue of the patients with lupus nephritis expressed CCR4, but not CCR5. CONCLUSION: These results suggest that CCR4+ T lymphocytes in peripheral blood, which represent Th2 cells, preferentially migrate into the renal tissue of patients with lupus nephritis. The maldistribution of CCR4+ T lymphocytes might be involved in the pathogenesis of lupus nephritis.