Disparate phospho-Smad2 levels in advanced type 2 diabetes patients with diabetic nephropathy and early experimental db/db mouse model.

Uncontrolled activation of transforming growth factor beta (TGF-ß) family members is hypothesized to participate in type 2 diabetes (T2D) dependent diabetic nephropathy (DN). We evaluated and compared downstream activation of the Smad2-signaling pathway in kidney samples from T2D patients to kidneys from the T2D model of leptin receptor deficient db/db mouse. Furthermore, expression of TGF-ß family members was evaluated to elucidate molecular mechanisms in the mouse model. Kidney samples from patients with advanced stages of DN showed elevated pSmad2 staining whereas db/db mouse kidneys surprisingly showed a decrease in pSmad2 in the tubular compartment. Structurally, kidney tissue showed dilated tubules and expanded glomeruli, but no clear fibrotic pattern was found in the diabetic mice. Selective TGF-ß family members were up-regulated at the mRNA level. Antagonists of bone morphogenetic protein (BMP) ligands, such as Gremlin1, USAG1 and Sclerostin, were strongly up-regulated suggesting a dampening effect on BMP pathways. Together, these results indicate a lack of translation from T2D patient kidneys to the db/db model with regards to Smad signaling pathway. It is plausible that a strong up-regulation of BMP antagonizing factors account for the lack of Smad1/5/8 activation, in spite of increased expression of several BMP members.

IL-20 contributes to low grade inflammation and weight gain in the Psammomys obesus.

The metabolic syndrome has been demonstrated in gene deficient animals, e.g. db/db mice, to include a systemic inflammation leading to insulin resistance, obesity and type 2 diabetes (T2D). To determine the importance of inflammation in obesity and diabetes, in a normal non-genetically modified species, an intervention study with neutralizing anti-IL-20 antibodies was conducted in the spontaneous T2D model Psammomys obesus. All IL-20 receptor chains were expressed on protein level in the Psammomys obesus. Neutralization of IL-20 did not modulate blood glucose, HbA1c, insulin levels or lymphocyte numbers after five weeks treatment although a trend to reduced weight gain rate was observed upon anti-IL-20 treatment. Inhibition of IL-20 significantly increased the number of CD11bhigh/low cells and the CD11bGr-1int myeloid derived suppressor cells in the spleen. Importantly, although the number of M1-like monocytes remained unchanged the M1-like marker CD11c expression level was reduced on the cells upon anti-IL-20 treatment. Anti-IL-20 treatment reduced both TLR4 and CCR2b expression on the macrophages upon treatment. Further, a marked shift in the protein signature in the pancreatic tissue after anti-IL-20 treatment was observed including enhanced expression of CXCL12, TIMP-1 and IL-10 while IL-1ß, CXCL4, PEDF and ADAMTS1 were reduced. In conclusion, we describe for the first time the systemic immune response in the diabetic Psammomys obesus. Neutralizing IL-20 modulated the myeloid compartment, the adaptive immunity, and local expression of proteins in the diabetic pancreatic tissue as well as improved on weight gain and hence may place IL-20 as a cytokine to be considered in obesity.

Smad2 Phosphorylation in Diabetic Kidney Tubule Epithelial Cells Is Associated with Modulation of Several Transforming Growth Factor-ß Family Members.

BACKGROUND: The role of transforming growth factor-ß (TGF-ß) has recently gained much attention in diabetic nephropathy and kidney fibrosis. In this study, we extend this to an assessment of transcriptional regulation of the entire TGF-ß superfamily in kidneys from diabetic vs. healthy mice. In order to study the translation between mouse model and patients, we evaluated the signature of phosphorylated Sma- and Mad-related protein 2 (pSmad2), as molecular marker of TGF-ß/activin activity, in the kidneys of streptozotocin (STZ)-treated mice compared to that of type 1 diabetes (T1D) patients. METHODS: Patterns of pSmad2 were determined in kidneys from T1D patients with progressed diabetic nephropathy (DN), defined by hyperglycemia, microalbuminuria, and increased levels of serum creatinine. They were compared to changes seen in the STZ-induced DN mouse model. This was studied by immunohistochemistry (IHC) with an antibody specific for pSmad2. Diabetic mice were also characterized by pSmad1/5/8 (IHC), pSmad2/3 (flow cytometry), and TGF-ß family members including bone morphogenetic protein (BMP)-like proteins (quantitative real-time polymerase chain reaction [qPCR]). RESULTS: Renal tubules in DN patients and in STZ mice showed upregulation of pSmad2 concomitant with significantly enlarged distal tubule lumens (p < 0.0001). Renal-derived CD11b+ cells from STZ mice showed elevated pSmad2/3, while endothelial cells had reduced pSmad2/3 levels. No pSmad1/5/8 was observed in the tubule compartment of STZ-treated mice. On total kidney mRNA level, a signature favoring activation of the TGF-ß/activin pathway and inhibition of the BMP pathway was demonstrated by qPCR. CONCLUSION: Although the pre-clinical DN model lacks the features of fibrosis present in human DN, both species show induction of a local milieu favoring pSmad2 signaling, which may be useful as a disease biomarker in pre-clinical models.

Liraglutide Reduces Both Atherosclerosis and Kidney Inflammation in Moderately Uremic LDLr-/- Mice.

Chronic kidney disease (CKD) leads to uremia. CKD is characterized by a gradual increase in kidney fibrosis and loss of kidney function, which is associated with a progressive increase in risk of atherosclerosis and cardiovascular death. To prevent progression of both kidney fibrosis and atherosclerosis in uremic settings, insight into new treatment options with effects on both parameters is warranted. The GLP-1 analogue liraglutide improves glucose homeostasis, and is approved for treatment of type 2 diabetes. Animal studies suggest that GLP-1 also dampens inflammation and atherosclerosis. Our aim was to examine effects of liraglutide on kidney fibrosis and atherosclerosis in a mouse model of moderate uremia (5/6 nephrectomy (NX)). Uremic (n = 29) and sham-operated (n = 14) atherosclerosis-prone low density lipoprotein receptor knockout mice were treated with liraglutide (1000 µg/kg, s.c. once daily) or vehicle for 13 weeks. As expected, uremia increased aortic atherosclerosis. In the remnant kidneys from NX mice, flow cytometry revealed an increase in the number of monocyte-like cells (CD68+F4/80-), CD4+, and CD8+ T-cells, suggesting that moderate uremia induced kidney inflammation. Furthermore, markers of fibrosis (i.e. Col1a1 and Col3a1) were upregulated, and histological examinations showed increased glomerular diameter in NX mice. Importantly, liraglutide treatment attenuated atherosclerosis (~40%, p < 0.05) and reduced kidney inflammation in NX mice. There was no effect of liraglutide on expression of fibrosis markers and/or kidney histology. This study suggests that liraglutide has beneficial effects in a mouse model of moderate uremia by reducing atherosclerosis and attenuating kidney inflammation.

Bone marrow-derived and peritoneal macrophages have different inflammatory response to oxLDL and M1/M2 marker expression - implications for atherosclerosis research.

Macrophages are heterogeneous and can polarize into specific subsets, e.g. pro-inflammatory M1-like and re-modelling M2-like macrophages. To determine if peritoneal macrophages (PEMs) or bone marrow derived macrophages (BMDMs) resembled aortic macrophages from ApoE-/- mice, their M1/M2 phenotype, inflammatory status, and lipid metabolism signatures were compared. oxLDL accumulation was similar in PEMs and BMDMs. On protein expression level, BMDMs showed an M2-like CD206highCD11clow profile, while cholesterol loading led to enhanced CD11c expression and reduced MCP-1 secretion. In contrast, PEMs expressed low levels of CD206 and CD11c, and responded to cholesterol loading by increasing CD11c expression and MCP-1 secretion. mRNA expression of M1/M2 markers was higher in PEMS than BMDMs, while lipid metabolism genes were similarly expressed. Whole aorta flow cytometry showed an accumulation of M2-like CD206highCD11clow macrophages in advanced versus early atherosclerotic disease in ApoE-/- mice. In isolated lesions, mRNA levels of the M2 markers Socs2, CD206, Retnla, and IL4 were downregulated with increasing disease severity. Likewise, mRNA expression of lipid metabolism genes (SREBP2, ACSL1, SRB1, DGAT1, and cpt1a) was decreased in advanced versus early lesions. In conclusion, PEMs and BMDMs are phenotypically distinct and differ from macrophages in lesions with respect to expression of M1/M2 markers and lipid metabolism genes.

Impaired coronary microcirculation in type 2 diabetic patients is associated with elevated circulating regulatory T cells and reduced number of IL-21R⁺ T cells.

BACKGROUND: Low-grade systemic inflammation is considered to participate in the progression of type 2 diabetes (T2D) and in diabetic complications. METHODS: To determine if circulating leukocytes were abnormally regulated in T2D patients, 8-color flow-cytometry (FACS) analysis was performed in a cross-sectional study of 37 T2D patients and 16 controls. Data obtained from the FACS analysis were compared to coronary flow reserve (CFR), assessed by Rb(82)-PET-imaging, to uncover inflammatory signatures associated with impaired CFR. RESULTS: Presence of T2D was associated with T cell attenuation characterized by reduced overall T cell, Th17, IL-21R(+), Treg's and TLR4(+) T cells, while the monocyte population showed enhanced TLR4 expression. Further, our data revealed reduced M1-like CD11c expression in T2D which was associated with impaired CFR. In contrast, we show, for the first time in T2D, increased TLR4 expression on CD8 T cells, increased Treg cell number and Treg maturation and reduced IL-21R expression on CD8 T cells to be functionally associated with impaired CFR. CONCLUSIONS: Our demonstration that HbA1c inversely correlates to several T cell populations suggests that T cells may play disease modulating roles in T2D. Further, the novel association between impaired CFR and regulatory T cells and IL-21R(+) T cells imply an intricate balance in maintaining tissue homeostasis in vascular diabetic complications.

Neutralizing Anti-IL20 Antibody Treatment Significantly Modulates Low Grade Inflammation without Affecting HbA1c in Type 2 Diabetic db/db Mice.

Low grade inflammation is present in pre-clinical and human type 2 diabetes. In this process, several cytokines like IL-1ß and inflammatory cells like macrophages are activated and demonstrated to participate to the disease initiation and progression. IL-20 is a cytokine known to play non-redundant roles in progression of several inflammatory diseases. To address the therapeutic effect of inhibiting the IL-20 pathway in diabetes, diabetic db/db mice were treated with neutralizing anti-IL20 antibodies in vivo and both metabolic and inflammatory parameters were followed. Diabetic islets expressed the IL-20 cytokine and all IL-20 receptor components in elevated levels compared to resting non-diabetic islets. Islets were responsive to ex vivo IL-20 stimulation measured as SOCS induction and KC and IL-6 production. Neutralizing anti-IL20 treatment in vivo had no effect on HbA1c or weight although the slope of blood glucose increase was lowered. In contrast, anti-IL20 treatment significantly reduced the systemic low-grade inflammation and modulated the local pancreatic immunity. Significant reduction of the systemic IL-1ß and MCP-1 was demonstrated upon anti-IL20 treatment which was orchestrated with a reduced RANTES, IL-16 and IL-2 but increased TIMP-1, MCP-1 and IL-6 protein expression locally in the pancreas. Interestingly, anti-IL20 treatment induced an expansion of the myeloid suppressor CD11bGr1int macrophage while reducing the number of CD8 T cells. Taken together, anti-IL20 treatment showed moderate effects on metabolic parameters, but significantly altered the low grade local and systemic inflammation. Hence, future combination therapies with anti-IL20 may provide beneficial therapeutic effects in type 2 diabetes through a reduction of inflammation.

Enalapril treatment increases T cell number and promotes polarization towards M1-like macrophages locally in diabetic nephropathy.

Diabetic nephropathy (DN) is a serious complication of longstanding diabetes affecting up to 30% of all diabetes patients and is the main cause of end-stage kidney disease globally. Current standard treatment e.g. ACE-inhibitors like enalapril merely offers a delay in the progression leading to DN. Herein, we describe in two preclinical models evidence to local effects on the inflammatory signatures after intervention treatment with enalapril which provides enhanced understanding of the mechanism of ACE inhibitors. Enalapril transiently reduced albuminuria in both the db/db and the STZ-induced DN models with established disease, without modulating the HbA1c%. Albuminuria was strongly associated with loss of leukocytes, particularly B cells, but also of sub-populations of macrophages and CD4(+) T cells. The remaining kidney macrophages were polarized into a M2-like sub-population with reduced surface expression of the M1-like macrophage marker CD11c and enhanced expression of galectin-3. Enalapril treatment counteracted the reduction of leukocytes in the diabetic kidney towards levels noted in the non-diabetic kidney. Particularly, a subset of macrophages was increased and a clear expansion of CD4(+) and CD8(+) T cells was observed. However, enalapril failed to modulate the B cell compartment. Interestingly, enalapril treatment resulted in a re-polarization of the macrophages towards a M1-like phenotype characterized by elevated levels of CD11c with moderate down-regulation of the M2 marker galectin-3. The data demonstrate that ACE inhibition in pre-clinical models of DN shows a transient beneficial effect on albuminuria which is unexpectedly associated with restoration of T cells and M1-like macrophages in the kidney.

Reduction of specific circulating lymphocyte populations with metabolic risk factors in patients at risk to develop type 2 diabetes.

Low-grade inflammation, characterized by increased pro-inflammatory cytokine levels, is present in patients with obesity-linked insulin resistance, hyperglycemia and hyperlipidemia and considered to play a leading role to progression into type 2 diabetes (T2D). In adipose tissue in obese patients and in pancreatic islets in T2D patients cellular inflammation is present. However, the systemic leukocyte compartment and the circulating endothelial/precursor compartment in patients at risk to develop T2D has so far not been analyzed in detail. To address this, peripheral blood cells from a cohort of 20 subjects at risk to develop diabetes with normal to impaired glucose tolerance were analyzed by flow cytometry using a wide range of cellular markers and correlated to known metabolic risk factors for T2D i.e. fasting plasma glucose (FPG), 2 h plasma glucose (2 h PG), HbA1c, body mass index (BMI), homeostasis model assessment of ß-cell function (HOMA-B), homeostasis model assessment of insulin sensitivity (HOMA-IS) and fasting insulin (FI). The four highest ranked cell markers for each risk factor were identified by random forest analysis. In the cohort, a significant negative correlation between the number of TLR4(+) CD4 T cells and increased FPG was demonstrated. Similarly, with increased BMI the frequency of TLR4(+) B cells was significantly decreased, as was the frequency of IL-21R(+) CD4 T cells. Unlinked to metabolic risk factors, the frequency of regulatory T cells was reduced and TLR4(+) CD4 T cells were increased with age. Taken together, in this small cohort of subjects at risk to develop T2D, a modulation of the circulating immune cell pool was demonstrated to correlate with risk factors like FPG and BMI. This may provide novel insights into the inflammatory mechanisms involved in the progression to diabetes in subjects at risk.

Macrophage contact dependent and independent TLR4 mechanisms induce ß-cell dysfunction and apoptosis in a mouse model of type 2 diabetes.

Type 2 diabetes (T2D) is evolving into a global disease and patients have a systemic low-grade inflammation, yet the role of this inflammation is still not established. One plausible mechanism is enhanced expression and activity of the innate immune system. Therefore, we evaluated the expression and the function of the toll-like receptor 4 (TLR4) on pancreatic ß-cells in primary mouse islets and on the murine ß-cell line MIN6 in the presence or absence of macrophages. Diabetic islets have 40% fewer TLR4 positive ß-cells, but twice the number of TLR4 positive macrophages as compared to healthy islets. Healthy and diabetic islets respond to a TLR4 challenge with enhanced production of cytokines (5-10-fold), while the TLR4 negative ß-cell line MIN6 fails to produce cytokines. TLR4 stimulation induces ß-cell dysfunction in mouse islets, measured as reduced glucose stimulated insulin secretion. Diabetic macrophages from 4-months old mice have acquired a transient enhanced capacity to produce cytokines when stimulated with LPS. Interestingly, this is lost in 6-months old diabetic mice. TLR4 activation alone does not induce apoptosis in islets or MIN-6 cells. In contrast, macrophages mediate TLR4-dependent cell-contact dependent (3-fold) as well as cell-contact independent (2-fold) apoptosis of both islets and MIN-6 cells. Importantly, diabetic macrophages have a significantly enhanced capacity to induce ß-cell apoptosis compared to healthy macrophages. Taken together, the TLR4 responsiveness is elevated in the diabetic islets and mainly mediated by newly recruited macrophages. The TLR4 positive macrophages, in both a cell-contact dependent and independent manner, induce apoptosis of ß-cells in a TLR4 dependent fashion and TLR4 activation directly induces ß-cell dysfunction. Thus, targeting either the TLR4 pathway or the macrophages provides a novel attractive treatment regime for T2D.

Accumulation of M1-like macrophages in type 2 diabetic islets is followed by a systemic shift in macrophage polarization.

Human T2D is characterized by a low-grade systemic inflammation, loss of ß-cells, and diminished insulin production. Local islet immunity is still poorly understood, and hence, we evaluated macrophage subpopulations in pancreatic islets in the well-established murine model of T2D, the db/db mouse. Already at 8 weeks of disease, on average, 12 macrophages were observed in the diabetic islets, whereas only two were recorded in the nondiabetic littermates. On a detailed level, the islet resident macrophages increased fourfold compared with nondiabetic littermates, whereas a pronounced recruitment (eightfold) of a novel subset of macrophages (CD68+F4/80-) was observed. The majority of the CD68+F4/80+ but only 40% of the CD68+F4/80- islet macrophages expressed CD11b. Both islet-derived macrophage subsets expressed moderate MHC-II, high galectin-3, and low CD80/CD86 levels, suggesting the cells to be macrophages rather than DCs. On a functional level, the vast majority of the macrophages in the diabetic islets was of the proinflammatory, M1-like phenotype. The systemic immunity in diabetic animals was characterized by a low-grade inflammation with elevated cytokine levels and increase of splenic cytokine, producing CD68+F4/80- macrophages. In late-stage diabetes, the cytokine signature changed toward a TGF-ß-dominated profile, coinciding with a significant increase of galectin-3-positive macrophages in the spleen. In summary, our results show that proinflammatory M1-like galectin-3+ CD80/CD86(low) macrophages invade diabetic islets. Moreover, the innate immunity matures in a diabetes-dependent manner from an initial proinflammatory toward a profibrotic phenotype, supporting the concept that T2D is an inflammatory disease.

Orally bioavailable allosteric CCR8 antagonists inhibit dendritic cell, T cell and eosinophil migration.

The chemokine receptor CCR8 is associated with asthma. Herein, we describe that both mature and immature dendritic cells (DC) express CCR8, whereas only mature DC migrate towards CCL1. Moreover, transient LPS challenge significantly down-regulates CCR8 expression hence attenuating CCL1 chemotaxis. To inhibit CCR8 pathophysiology, we recently developed a novel series of small molecule CCR8 antagonists containing a diazaspiroundecane scaffold, which had micromolar potency. However, these first generation antagonists had high lipophilicity that endowed the compounds with poor physicochemical properties, and were thus not suitable for further development. By introducing polar bicyclic groups on the N-benzyl substituent and building in further polar interactions on the amide group we now show second generation diazospiroundecane antagonists with significantly improved overall properties. Potency is substantially improved from micromolar to nanomolar potency in CCR8 binding and inhibition of chemotaxis in human primary T cells, DC and in an eosinophil cell line. In addition to high potency, the most attractive antagonist, AZ084 showed excellent selectivity, high metabolic stability in vitro and an attractive in vivo PK profile with a long half-life in rat. Interestingly, in ligand saturation experiments and in wash-off experiments, CCL1 was shown to have two binding sites to CCR8 with K(d) at 1.2/68pM respectively, and on-off rates of 0.004 and 0.0035/0.02pMmin, respectively. The lead antagonist, AZ084, appears to act as an allosteric inhibitor with a K(i) at 0.9nM. Taken together, we herein report a novel oral allosteric CCR8 antagonist with predicted low once-daily dosing capable of potent inhibition of both human T cell and DC functions.

CCR8 signaling influences Toll-like receptor 4 responses in human macrophages in inflammatory diseases.

CCR8 immunity is generally associated with Th2 responses in allergic diseases. In this study, we demonstrate for the first time a pronounced attenuated influx of macrophages in ovalbumin (OVA)-challenged CCR8 knockout mice. To explore whether macrophages in human inflamed lung tissue also were CCR8 positive, human lung tissue from patients with chronic obstructive pulmonary disease (COPD) was evaluated. Indeed, CCR8 expression was pronounced in invading monocytes/macrophages from lungs of patients with Global Initiative for Obstructive Lung Disease (GOLD) stage IV COPD. Given this expression pattern, the functional role of CCR8 on human macrophages was evaluated in vitro. Human peripheral blood monocytes expressed low levels of CCR8, while macrophage colony-stimulating factor (M-CSF)-derived human macrophages expressed significantly elevated surface levels of CCR8. Importantly, CCL1 directly regulated the expression of CD18 and CD49b and hence influenced the adhesion capacity of human macrophages. CCL1 drives chemotaxis in M-CSF-derived macrophages, and this could be completely inhibited by lipopolysaccharide (LPS). Whereas both CCL1 and LPS monotreatment inhibited spontaneous superoxide release in macrophages, CCL1 significantly induced superoxide release in the presence of LPS in a dose-dependent manner. Finally, CCL1 induced production of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) and could inhibit LPS-induced cytokine production in a dose-dependent manner. Our data demonstrate, for the first time, the presence of CCR8 on inflammatory macrophages in human COPD lung tissue. Importantly, the functional data from human macrophages suggest a potential cross talk between the CCR8 and the Toll-like receptor 4 (TLR4) pathways, both of which are present in COPD patients.

RhoB deficiency in thymic medullary epithelium leads to early thymic atrophy.

RhoB, a member of the Rho subfamily of small GTPases, mediates diverse cellular functions, including cytoskeletal organization, cell transformation and vesicle trafficking. The thymus undergoes progressive decline in its structure and function after puberty. We found that RhoB was expressed in thymic medullary epithelium. To investigate a role of RhoB in the regulation of thymic epithelial organization or thymocyte development, we analyzed the thymi of RhoB-deficient mice. RhoB-deficient mice were found to display earlier thymic atrophy. RhoB deficiency showed significant reductions in thymus weight and cellularity, beginning as early as 5 weeks of age. The enhanced expression of TGF-ß receptor type II (TGFßRII) in thymic medullary epithelium was observed in RhoB-null mice. In addition, the expression of fibronectin, which is shown to be regulated by TGF-ß signaling, was accordingly increased in the mutant thymic medulla. Since there is no age-related change of RhoB expression in the thymus, it is unlikely that RhoB in thymic epithelium directly contributes to age-related thymic involution. Nevertheless, our findings strongly support a physiological role of RhoB in regulation of thymus development and maintenance through the inhibition of TGF-ß signaling in thymic medullary epithelium.

Small molecule antagonists of CCR8 inhibit eosinophil and T cell migration.

In this study, we demonstrate that in addition to T lymphocytes, human naïve eosinophils and the differentiated eosinophil-like cell line, AML14.3D10 express CCR8 and respond to CCL1 through CCR8 engagement. The responsiveness of cells was dependent on maturation stage, since CCL1 induced pronounced chemotaxis only in differentiated CCR8 positive AML14.3D10 cells. Despite the low CCR8 surface expression, human naïve eosinophils respond with a chemotaxis to high concentration CCL1. We further describe that Th2 clones in a maturation dependent fashion produce autocrine CCL1, which renders them unresponsive to further stimulation. An innovative method to enrich primary CCR8 reactive T cells was developed which demonstrates that primary peripheral CCR8 expressing T cells respond significantly to CCL1. We have developed novel small molecule CCR8 antagonists that are effective in inhibiting calcium mobilization and chemotaxis in differentiated AML cells as well as in human primary CCR8 positive T cells. Importantly, we demonstrate that the compounds can be divided into two subgroups: (i) compounds that are functional agonists for calcium mobilization and chemotaxis (ii) compounds that are pure antagonists. We demonstrate that agonism of these compounds does not correlate with their antagonistic potency. Taken together, we have identified a novel set of CCR8 compounds with antagonistic properties that inhibit CCL1 driven chemotaxis in both CCR8 expressing eosinophils as well as primary human T cells.

Increasing selectivity of CC chemokine receptor 8 antagonists by engineering nondesolvation related interactions with the intended and off-target binding sites.

The metabolic stability and selectivity of a series of CCR8 antagonists against binding to the hERG ion channel and cytochrome Cyp2D6 are studied by principal component analysis. It is demonstrated that an efficient way of increasing metabolic stability and selectivity of this series is to decrease compound lipophilicity by engineering nondesolvation related attractive interactions with CCR8, as rationalized by three-dimensional receptor models. Although such polar interactions led to increased compound selectivity, such a strategy could also jeopardize the DMPK profile of compounds. However, once increased potency is found, the lipophilicity can be readjusted by engineering hydrophobic substituents that fit to CCR8 but do not fit to hERG. Several such lipophilic fragments are identified by two-dimensional fragment-based QSAR analysis. Electrophysiological measurements and site-directed mutagenesis studies indicated that the repulsive interactions of these fragments with hERG are caused by steric hindrances with residue F656.

Deletion of exon I of SMAD7 in mice results in altered B cell responses.

The members of the TGF-beta superfamily, i.e., TGF-beta isoforms, activins, and bone morphogenetic proteins, regulate growth, differentiation, and apoptosis, both during embryonic development and during postnatal life. Smad7 is induced by the TGF-beta superfamily members and negatively modulates their signaling, thus acting in a negative, autocrine feedback manner. In addition, Smad7 is induced by other stimuli. Thus, it can fine-tune and integrate TGF-beta signaling with other signaling pathways. To investigate the functional role(s) of Smad7 in vivo, we generated mice deficient in exon I of Smad7, leading to a partial loss of Smad7 function. Mutant animals are viable, but significantly smaller on the outbred CD-1 mouse strain background. Mutant B cells showed an overactive TGF-beta signaling measured as increase of phosphorylated Smad2-positive B cells compared with B cells from wild-type mice. In agreement with this expected increase in TGF-beta signaling, several changes in B cell responses were observed. Mutant B cells exhibited increased Ig class switch recombination to IgA, significantly enhanced spontaneous apoptosis in B cells, and a markedly reduced proliferative response to LPS stimulation. Interestingly, LPS treatment reverted the apoptotic phenotype in the mutant cells. Taken together, the observed phenotype highlights a prominent role for Smad7 in development and in regulating the immune system's response to TGF-beta.

A hierarchical order of factors in the generation of FLK1- and SCL-expressing hematopoietic and endothelial progenitors from embryonic stem cells.

The receptor tyrosine kinase FLK1 and the transcription factor SCL play crucial roles in the establishment of hematopoietic and endothelial cell lineages in mice. We have previously used an in vitro differentiation model of embryonic stem (ES) cells and demonstrated that hematopoietic and endothelial cells develop via sequentially generated FLK1(+) and SCL(+) cells. To gain a better understanding of cellular and molecular events leading to hematopoietic specification, we examined factors necessary for FLK1(+) and SCL(+) cell induction in serum-free conditions. We demonstrate that bone morphogenetic protein (BMP) 4 was required for the generation of FLK1(+) and SCL(+) cells, and that vascular endothelial growth factor (VEGF) was necessary for the expansion and differentiation of SCL-expressing hematopoietic progenitors. Consistently, Flk1-deficient ES cells responded to BMP4 and generated TER119(+) and CD31(+) cells, but they failed to expand in response to VEGF. The Smad1/5 and map kinase pathways were activated by BMP4 and VEGF, respectively. The overexpression of SMAD6 in ES cells resulted in a reduction of FLK1(+) cells. In addition, a MAP kinase kinase 1 specific inhibitor blocked the expansion of SCL(+) cells in response to VEGF. Finally, VEGF mediated expansion of hematopoietic and endothelial cell progenitors was inhibited by TGFbeta1, but was augmented by activin A. Our studies suggest that hematopoietic and endothelial commitment from the mesoderm occurs via BMP4-mediated signals and that expansion and/or differentiation of such progenitors is achieved by an interplay of VEGF, TGFbeta1 and activin A signaling.

Transforming growth factor-beta- and Activin-Smad signaling pathways are activated at distinct maturation stages of the thymopoeisis.

Members of the transforming growth factor (TGF)-beta family play pivotal roles in the control of differentiation, proliferation and tolerance in peripheral T cells. Recently, they have been implicated in thymic selection, but their role is so far not well characterized. In the present study, we demonstrate that specific thymocyte populations are under the influence of either the TGF-beta and/or Activin pathway, and transduce signals into the nucleus via phosphorylated Smad2 (pSmad2). Thymocytes in the medulla and in the subcapsular zone expressed nuclear translocated pSmad2, a hallmark of active TGF-beta/Activin receptor signaling. When analyzed at the cellular level, the pSmad2(+) cells were confined to the double-negative (DN) and single-positive (SP) subpopulations. Moreover, the most immature DN thymocytes (CD44(+)CD25(-) and CD44(+)CD25(+)) expressed higher levels of pSmad2 compared to the more mature DN. In vitro stimulation demonstrated that pure CD44(+)CD25(-), CD44(+)CD25(+) and CD44(+)CD25(+) thymocytes respond to ActivinA, while the mature CD4(+) and CD8(+) SP thymocytes respond to TGF-beta stimulation measured as enhanced phosphorylation of Smad2. Double staining of pSmad2(+) cells with either the Activin type I receptor, ALK4, or the TGF-beta type I receptor, ALK5, demonstrated that pSmad2(+) DN cells exhibited high levels of immunoreactivity to ALK4 and moderate levels of immunoreactivity to the TGF-beta-responsive ALK5 receptor. In sharp contrast, the SP pSmad2(+) cells were predominately ALK5(+). Collectively, our results demonstrate that early and late thymocytes express pSmad2 in the nuclei in vivo. The functional experiments in vitro suggest that members of the TGF-beta family (TGF-beta or Activin) may play important non-redundant roles during different stages of thymopoiesis.

Stimulation of Id1 expression by bone morphogenetic protein is sufficient and necessary for bone morphogenetic protein-induced activation of endothelial cells.

BACKGROUND: Bone morphogenetic proteins (BMPs) are multifunctional proteins that regulate the proliferation, differentiation, and migration of a large variety of cell types. Like other members of the transforming growth factor-beta family, BMPs elicit their cellular effects through activating specific combinations of type I and type II serine/threonine kinase receptors and their downstream effector proteins, which are termed Smads. In the present study, we investigated BMP receptor/Smad expression and signaling in endothelial cells (ECs) and examined the effects of BMP on EC behavior. METHODS AND RESULTS: Immunohistochemical analysis of tissue sections of human colon and mouse heart and aorta showed that BMP receptors are expressed in ECs in vivo. Bovine aortic ECs and mouse embryonic ECs were found to express BMP receptors and their Smads. BMP receptor activation induced the phosphorylation of specific Smad proteins and promoted EC migration and tube formation. Id1 was identified as a BMP/Smad target in ECs. Ectopic expression of Id1 mimicked BMP-induced effects. Importantly, specific interference with Id1 expression blocked BMP-induced EC migration. CONCLUSIONS: The BMP/Smad pathway can potently activate the endothelium. Id1 expression is strongly induced by BMP in ECs. Ectopic expression of Id1 induces EC migration and tube formation. Moreover, Id1 played a critical role in mediating BMP-induced EC migration.