Toll-like receptors in domestic animals

Toll-like receptors are pattern recognition receptors with which hosts recognize pathogen-associated molecular patterns (PAMP). This recognition process is translated rapidly into a meaningful defense reaction. This form of innate host defense is preserved in the animal kingdom: invertebrates heavily depend on it; higher vertebrates also have an adaptive immune system. Both adaptive and innate immune systems are intertwined in that the former also depends on an intact innate recognition and response system. Members of the TLR system cover recognition of parasitic, bacterial or viral germs. Due to the constraints imposed by the necessity to recognize PAMP and to interact with downstream signaling molecules, the TLR system is relatively conserved in evolution. Nevertheless, subtle species differences have been reported for several mammalian TLR members. Examples of this will be given. In all mammalian species investigated, part of the coding sequence is available for the most important TLR members, thus allowing study of expression of these TLR members in various tissues by reverse-transcription polymerase chain reaction in its classical (RT-PCR) and quantitative real time RT-PCR (qRT-PCR) form. In some species, the whole coding sequences of the most important or even all TLR members are known. This allows construction of cDNA and transfection of common host cells, thus permitting functional studies. Extensive investigations were devoted to the study of non-synonymous single nucleotide polymorphisms. In a few cases, expression of a given amino acid in the extracellular (ligand-binding) portion of TLR members could be associated with infectious diseases. This will be discussed below.

Comparative analysis of canine monocyte- and bone-marrow-derived dendritic cells

Dendritic cells (DC) represent a heterogeneous cell family of major importance for innate immune responses against pathogens and antigen presentation during infection, cancer, allergy and autoimmunity. The aim of the present study was to characterize canine DC generated in vitro with respect to their phenotype, responsiveness to toll-like receptor (TLR) ligands and T-cell stimulatory capacity. DC were derived from monocytes (MoDC) and from bone marrow hematopoietic cells cultured with either Flt3-ligand (FL-BMDC) or with GM-CSF (GM-BMDC). All three methods generated cells with typical DC morphology that expressed CD1c, CD11c and CD14, similar to macrophages. However, CD40 was only found on DC, CD206 on MPhi and BMDC, but not on monocytes and MoDC. CD1c was not found on monocytes but on all in vitro differentiated cells. FL-BMDC and GM-BMDC were partially positive for CD4 and CD8. CD45RA was expressed on a subset of FL-BMDC but not on MoDC and GM-BMDC. MoDC and FL-DC responded well to TLR ligands including poly-IC (TLR2), Pam3Cys (TLR3), LPS (TLR4) and imiquimod (TLR7) by up-regulating MHC II and CD86. The generated DC and MPhi showed a stimulatory capacity for lymphocytes, which increased upon maturation with LPS. Taken together, our results are the basis for further characterization of canine DC subsets with respect to their role in inflammation and immune responses.

Expression of Toll-like receptor 2 in duodenal biopsies from dogs with inflammatory bowel disease is associated with severity of disease

There is growing evidence that aberrant innate immune responses towards the bacterial flora of the gut play a role in the pathogenesis of canine inflammatory bowel disease (IBD). Toll-like receptors (TLR) play an important role as primary sensors of invading pathogens and have gained significant attention in human IBD as differential expression and polymorphisms of certain TLR have been shown to occur in ulcerative colitis (UC) and Crohn's disease (CD). The aim of the current study was to evaluate the expression of two TLR important for recognition of commensals in the gut. TLR2 and TLR4 mRNA expression in duodenal biopsies from dogs with IBD was measured and correlated with clinical and histological disease severity. Endoscopic duodenal biopsies from 20 clinical cases and 7 healthy control dogs were used to extract mRNA. TLR2 and TLR4 mRNA expression was assessed using quantitative real-time PCR. TLR2 mRNA expression was significantly increased in the IBD dogs compared to controls, whereas TLR4 mRNA expression was similar in IBD and control cases. In addition, TLR2 mRNA expression was mildly correlated with clinical severity of disease, however, there was no correlation between TLR2 expression and histological severity of disease.

Human monocytoid cells as a model to study Toll-like receptor-mediated activation

THP-1 2A9, a subclone of the monocytoid cell line THP-1 and known to be exquisitely sensitive to LPS, was tested for TNF production following triggering by excess doses of TLR ligands. TLR2, TLR4 and TLR5 agonists, but neither TLR3 nor TLR9 agonists, induced TNF production. When used at lower concentrations, priming by calcitriol strongly influenced the sensitivity of cells to LPS and different TLR2 triggers (lipoteichoic acid (LTA), trispalmitoyl-cysteyl-seryl-lysyl-lysyl-lysyl-lysine (Pam3Cys) and peptidoglycan (PGN)). Priming by calcitriol failed to modulate TLR2 and TLR4 mRNA and cell surface expression of these receptors. TNF signals elicited by TLR2 agonists were blocked by the TLR-specific antibody 2392. CD14-specific antibodies showed variable effects. CD14-specific antibodies inhibited TNF induction by LTA. High concentrations partially inhibited TNF induction by Pam3Cys. The same antibodies failed to inhibit TNF induction by PGN. Thus, THP-1 2A9 cells respond by TNF production to some, but not all TLR agonists, and the wide variety of putative TLR2 agonists interact to variable degrees also with other cell-surface-expressed binding sites such as CD14. THP-1 2A9 cells might provide a model by which to investigate in more detail the interaction of pathogen-associated molecular patterns and monocytoid cell-surface-expressed pattern recognition receptors.

Impact of vessel size on outcome after implantation of sirolimus-eluting and paclitaxel-eluting stents: a subgroup analysis of the SIRTAX trial

OBJECTIVES: We assessed the impact of vessel size on angiographic and long-term clinical outcome after percutaneous coronary intervention (PCI) with sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES) within a randomized trial (SIRTAX [Sirolimus-Eluting Stent Compared With Paclitaxel-Eluting Stent for Coronary Revascularization]). BACKGROUND: Percutaneous coronary intervention in small-vessel disease is associated with an increased risk of major adverse cardiac events (MACE). METHODS: A total of 1,012 patients were randomly assigned to treatment with SES (n = 503) or PES (n = 509). A stratified analysis of angiographic and clinical outcome was performed up to 2 years after PCI according to size of the treated vessel (reference vessel diameter < or =2.75 vs. >2.75 mm). RESULTS: Of 1,012 patients, 370 patients (37%) with 495 lesions underwent stent implantation in small vessels only, 504 patients (50%) with 613 lesions in large vessels only, and 138 patients (14%) with 301 lesions in both small and large vessels (mixed). In patients with small-vessel stents, SES reduced MACE by 55% (10.4% vs. 21.4%; p = 0.004), mainly driven by a 69% reduction of target lesion revascularization (TLR) (6.0% vs. 17.7%; p = 0.001) compared with PES at 2 years. In patients with large- and mixed-vessel stents, rates of MACE (large: 10.4% vs. 13.1%; p = 0.33; mixed: 16.7% vs. 18.0%; p = 0.83) and TLR (large: 6.9% vs. 8.6%; p = 0.47; mixed: 16.7% vs. 15.4%; p = 0.86) were similar for SES and PES. There were no significant differences with respect to death and myocardial infarction between the 3 groups. CONCLUSIONS: Compared with PES, SES more effectively reduced MACE and TLR in small-vessel disease. Differences between SES and PES appear less pronounced in patients with large- and mixed-vessel disease. (The SIRTAX trial; http://clinicaltrials.gov/ct/show/NCT00297661?order=1; NCT00297661).

Small is beautiful: why profundaplasty should not be forgotten

BACKGROUND: Surgical profundaplasty (SP)is used mainly as an adjunct to endovascular management of peripheral vascular disease (PAD) today. Results from earlier series of profundaplasty alone have been controversial, especially regarding its hemodynamic effect. The question is: Can profundaplasty alone still be useful? Our aim was to evaluate its role in the modern management of vascular patients. METHODS: This was a retrospective outcome study. A consecutive series of 97 patients (106 legs) from January 2000 through December 2003 were included. In 55 (52%) legs, the superficial femoral artery was occluded. These patients were included in the current analysis. Of these patients 14 (25%) were female. Mean age was 71 ((11) years. Nineteen (35%) were diabetic. The indication for operation was claudication in 29 (53%), critical leg ischemia (CLI) in 26 (47%), either with rest pain in 17 (31%), or ulcer/gangrene in 9 (16%). Endarterectomy with patch angioplasty with bovine pericardium was performed in all cases. Mean follow-up was 33 ( 14 months. Mean preoperative ankle brachial index (ABI) was 0.6. Sustained clinical efficacy was defined as upward shift of 1 or greater on the Rutherford scale without repeat target limb revascularization (TLR) or amputation. Mortality, morbidity, need for TLR, or amputation were separate endpoints. RESULTS: Postoperatively, ABI was significantly improved (mean = 0.7), in 24 (44%) by more than 0.15. At three years, cumulative clinical success rate was 80%. Overall, patients with claudication had a better outcome than those with CLI (p = 0.04). Two (4%) major amputations and 2 (4%) minor ones were performed, all in patients with CLI. None of the 9 (16%) ulcers healed. CONCLUSION: Profundaplasty is still a valuable option for patients with femoral PAD and claudication without tissue loss. It is a straightforward procedure that combines good efficacy with low complication rates. Further endovascular treatment may be facilitated. It is not useful for patients with the combination of critical ischemia and tissue loss.

Two-year clinical outcome after implantation of sirolimus-eluting and paclitaxel-eluting stents in diabetic patients

Aims Percutaneous coronary intervention (PCI) in diabetic patients is associated with an increased risk of restenosis and major adverse cardiac events (MACE). We assessed the impact of diabetes on long-term outcome after PCI with sirolimus-eluting (SES) and paclitaxel-eluting (PES) stents. Methods and results In the SIRTAX trial, 1012 patients were randomized to treatment with SES (n = 503) or PES (n = 509). A stratified analysis of outcomes was performed according to the presence or absence of diabetes. Baseline characteristics were well balanced between SES and PES in patients with (N = 201) and without diabetes (N = 811). Clinical outcome was worse in diabetic compared with non-diabetic patients regarding death (9.0% vs. 4.1%, P = 0.004) and MACE (defined as cardiac death, myocardial infarction, or TLR; 19.9% vs. 12.7%, P = 0.007) at 2 years. Among diabetic patients, SES reduced MACE by 47% (14.8% vs. 25.8%, HR = 0.52, P = 0.05) and TLR by 61% (7.4% vs. 17.2%, HR = 0.39, P = 0.03) compared with PES at 2 years. Conclusion Diabetic patients have worse prognosis than non-diabetic patients undergoing PCI with DES. Among the diabetic patient population of this trial, SES reduce repeat revascularization procedures and MACE more effectively than PES and to a similar degree as in non-diabetic patients.

Elective implantation of sirolimus-eluting stents for bifurcated and non-bifurcated unprotected left main coronary artery lesions: clinical outcomes at one year

AIMS: Recent studies of drug-eluting stents for unprotected left main coronary artery (LMCA) disease have been encouraging. We examined the performance of sirolimus-eluting stents (SES) for this indication. METHODS AND RESULTS: This retrospective study included 228 consecutive patients (mean age = 68 +/- 11 years, 80.6% men, 26.3% diabetics) who underwent implantation of SES for de novo LMCA stenoses. The mean additive and logistic EuroSCOREs were 5.2 +/- 3.9 and 8.2 +/- 13.2, respectively. The main objective of this study was to measure the rate of major adverse cardiac events (MACE), including death, myocardial infarction and target lesion revascularisation (TLR) at 12 months. Other objectives were to measure the rates of in-hospital MACE and 12-month TLR. Outcomes in 143 patients with (BIF+ group), versus 84 patients without (BIF-group) involvement of the bifurcation were compared. The pre-procedural percent diameter stenosis (%DS) was 60.1 +/- 11.2 in the BIF+ versus 54.7 +/- 12.2% in the BIF- group (p=0.008), and decreased to 18.0 +/- 9.7 and 13.9 +/- 11.3%, respectively (ns), after SES implant. The overall in-hospital MACE rate was 3.5%, and similar in both subgroups. The 1-year MACE rate was 14.5% overall, 16.8% in the BIF+ and 10.7% in the BIF- subgroup (ns). CONCLUSIONS: SES implants in high-risk patients with LMCA stenoses were associated with a low 1-year MACE rate. Stenting of the bifurcation was associated with significant increases in neither mortality nor 1-year MACE rate.

Longest available clinical outcomes after drug-eluting stent implantation for unprotected left main coronary artery disease: the DELFT (Drug Eluting stent for LeFT main) Registry

OBJECTIVES: The purpose of this study was to investigate the long-term safety and efficacy of percutaneous coronary intervention (PCI) with drug-eluting stent (DES) implantation for unprotected left main coronary artery (ULMCA) disease. BACKGROUND: Long-term clinical outcomes after DES implantation for ULMCA disease have not yet been ascertained. METHODS: From April 2002 to April 2004, 358 consecutive patients who underwent PCI with DES implantation for de novo lesions on ULMCA were retrospectively selected and analyzed in 7 European and U.S. tertiary care centers. No patients were excluded from the analysis, and all patients had a minimum follow-up of 3 years. RESULTS: Technical success rate was 100%. Procedural success rate was 89.6%. After 3 years, major adverse cardiovascular events (MACE)-free survival in the whole population was 73.5%. According to the Academic Research Consortium definitions, cardiac death occurred in 9.2% of patients, and reinfarction, target lesion revascularization (TLR), and target vessel revascularization (TVR) occurred in 8.6%, 5.8%, and 14.2% of patients, respectively. Definite stent thrombosis occurred in 2 patients (specifically at 0 and 439 days). In elective patients, the 3-year MACE-free survival was 74.2%, with mortality, reinfarction, TLR, and TVR rates of 6.2%, 8.3%, 6.6%, and 16%, respectively. In the emergent group the 3-year MACE-free survival was 68.2%, with mortality, reinfarction, TLR, and TVR rates of 21.4%, 10%, 2.8%, and 7.1%, respectively. CONCLUSIONS: Routine DES implantation in ULMCA disease seems encouraging, with favorable long-term clinical results.

Diabetic patients treated for unprotected left main coronary artery disease with drug eluting stents: a 3-year clinical outcome study. The diabetes and drug eluting stent for LeFT main registry (D-DELFT)

AIMS: Diabetes mellitus (DM) plays an important role in the development of coronary artery disease. Although previous studies have associated drug-eluting stent (DES) implantation in diabetic patients with favourable clinical and angiographic outcomes, the very long-term efficacy of these devices in diabetic patients undergoing PCI for significant unprotected left main coronary artery (ULMCA) disease has not been established yet. METHODS AND RESULTS: Consecutive diabetic patients (n=100), who underwent elective PCI with DES for de novo lesions in an ULMCA between April 2002 and April 2004 in seven tertiary health care centres, were identified retrospectively and analysed. Consecutive non-diabetic patients (n=193), who underwent elective DES implantation for unprotected ULMCA disease, were selected as a control group. All patients were followed for at least 36 months. At 3-years follow-up, freedom from cardiac death ; myocardial infarction (CDMI), target lesion revascularisation (TLR) and target vessel revascularisation (TVR) did not differ significantly between groups. The adjusted freedom from major adverse cardiac events (MACE, defined as the occurrence of CD, MI or TVR) was 63.4% in the DM group and 77.6% in the controls (p<0.001). When divided into IDDM and NIDDM sub-groups, insulin-dependent DM (IDDM) but not non IDDM (NIDDM) patients had significantly lower freedom from CDMI, TLR, TVR and MACE compared to controls. CONCLUSIONS: These results suggest that major improvements in DES technology and pharmacotherapy are still required to improve clinical outcome and that the decision to perform percutaneous revascularisation in this subset of patients should be taken cautiously and on a case by case basis.

The complement inhibitor low molecular weight dextran sulfate prevents TLR4-induced phenotypic and functional maturation of human dendritic cells

Low molecular weight dextran sulfate (DXS) has been reported to inhibit the classical, alternative pathway as well as the mannan-binding lectin pathway of the complement system. Furthermore, it acts as an endothelial cell protectant inhibiting complement-mediated endothelial cell damage. Endothelial cells are covered with a layer of heparan sulfate (HS), which is rapidly released under conditions of inflammation and tissue injury. Soluble HS induces maturation of dendritic cells (DC) via TLR4. In this study, we show the inhibitory effect of DXS on human DC maturation. DXS significantly prevents phenotypic maturation of monocyte-derived DC and peripheral myeloid DC by inhibiting the up-regulation of CD40, CD80, CD83, CD86, ICAM-1, and HLA-DR and down-regulates DC-SIGN in response to HS or exogenous TLR ligands. DXS also inhibits the functional maturation of DC as demonstrated by reduced T cell proliferation, and strongly impairs secretion of the proinflammatory mediators IL-1beta, IL-6, IL-12p70, and TNF-alpha. Exposure to DXS leads to a reduced production of the complement component C1q and a decreased phagocytic activity, whereas C3 secretion is increased. Moreover, DXS was found to inhibit phosphorylation of IkappaB-alpha and activation of NF-kappaB. These findings suggest that DXS prevents TLR-induced maturation of human DC and may therefore be a useful reagent to impede the link between innate and adaptive immunity.

Impact of vessel size on angiographic and clinical outcomes of revascularization with biolimus-eluting stent with biodegradable polymer and sirolimus-eluting stent with durable polymer the LEADERS trial substudy

OBJECTIVES: We assessed the impact of vessel size on outcomes of stenting with biolimus-eluting degradable polymer stent (BES) and sirolimus-eluting permanent polymer stent (SES) within a randomized multicenter trial (LEADERS). BACKGROUND: Stenting of small vessels might be associated with higher rates of adverse events. METHODS: "All-comer" patients (n = 1,707) were randomized to BES and SES. Post-hoc-stratified analysis of angiographic and clinical outcomes at 9 months and 1 year, respectively, was performed for vessels with reference diameter 2.75 mm. RESULTS: Of 1,707 patients, 429 patients in the BES group with 576 lesions and 434 patients in the SES group with 557 lesions had only small vessels treated (50.6% of the patient cohort). In patients with small vessels there was no significant difference in overall major adverse cardiac events (MACE) rate (12.1% vs. 11.8%; p = 0.89) or target lesion revascularization (TLR) rate (9.6% vs. 7.4%; p = 0.26) between BES and SES. The MACE and TLR rates in the small-vessel patient population were higher than in the large-vessel population. The TLR rate was 9.6% versus 2.6%, and MACE rate was 12.1% versus 7.1% for small versus large vessels in the BES arm (TLR: hazard ratio [HR] = 3.724, p = 0.0013; MACE: HR = 1.720, p = 0.0412). In the SES arm, TLR was 7.4% versus 5.1%, and MACE was 11.8% versus 10.3% in small versus large vessels (TLR: HR = 1.435, p = 0.2594; MACE: HR = 1.149, p = 0.5546). CONCLUSIONS: Prevalence of small vessel disease is high in an "all-comer" population with higher TLR and MACE rates. The BES and SES seem equivalent in treatment outcomes of small vessels in this "all-comer" patient population.

Biolimus-eluting biodegradable polymer versus sirolimus-eluting permanent polymer stent performance in long lesions: results from the LEADERS multicentre trial substudy

AIMS: Lesion length remains a predictor of target lesion revascularisation and results of long lesion stenting remain poor. Sirolimus-eluting stents have been shown to perform better than paclitaxel eluting stents in long lesions. In this substudy of the LEADERS trial, we compared the performance of biolimus biodegradable polymer (BES) and sirolimus permanent polymer stents (SES) in long lesions. METHODS AND RESULTS: A total of 1,707 'all-comer' patients were randomly allocated to treatment with BES and SES. A stratified analysis of angiographic and clinical outcomes at nine months and one year, respectively was performed for vessels with lesion length <20 mm versus >20 mm (as measured by quantitative angiography).Of 1,707 patients, 592 BES patients with 831 lesions and 619 SES patients with 876 lesions had only short lesions treated. One hundred and fifty-three BES patients with 166 lesions and 151 SES patients with 162 lesions had long lesions. There were no significant differences in baseline clinical characteristics, except for higher number of patients with long lesions presenting with acute myocardial infarction in both stent groups. Long lesions tended to have lower MLD and greater percent diameter stenosis at baseline than short lesions. Late loss was greater for long lesions than short lesions. There was no statistically significant difference in late loss between BES and SES stents (0.32+/-0.69 vs 0.24+/-0.57, p=0.59). Binary in-segment restenosis was present in 23.2% versus 13.1% of long lesions treated with BES and SES, respectively (p=0.042). In patients with long lesions, the overall MACE rate was similar for BES and SES (17% vs 14.6%; p=0.62). There was a trend towards higher overall TLR rate with BES (12.4 % vs 6.0%; HR=2.06; p=0.07) and clinically driven TLR (10.5% vs 5.3%: HR 1.94; p=0.13). Rates of definite stent thrombosis were 3.3% in the long lesion group and 1.3-1.7 % in the short lesion group. CONCLUSIONS: BES and SES appear similar with respect to MACE in long lesions in this "all-comer" patient population. However, long lesions tended to have a higher rate of binary in-segment restenosis and TLR following BES than SES treatment.

TLR2 and TLR4 agonists induce production of the vasoactive peptide endothelin-1 by human dendritic cells

Endothelin-1 (ET-1) is mainly secreted by endothelial cells and acts as a potent vasoconstrictor. In addition ET-1 has also been shown to have pleiotropic effects on a variety of other systems including adaptive immunity. There are two main ET-1 receptors, ET(A) and ET(B), which have different tissue and functional distributions. Dendritic cells (DC) are pivotal antigen-presenting cells linking the innate with the adaptive immune system. DC are sentinels expressing pattern-recognition receptors, e.g. the toll-like receptors (TLR) for detecting danger signals released from pathogens or tissue injury. Here we show for the first time that stimulation of human monocyte-derived DC with exogenous as well as endogenous selective TLR4 and TLR2 agonists induces the production of ET-1 in a dose- and time-dependent manner. 'Alternative' activation of DC in the presence of 1alpha,25-dihydroxyvitamin D(3) results in a marked potentiation of the endothelin response, whereas prostaglandin E(2) or dexamethasone do not increase ET-1 production. Furthermore, chetomin, an inhibitor of the transcription factor hypoxia-inducible factor 1alpha (HIF-1alpha), prevents TLR-mediated secretion of ET-1. Surprisingly, stimulation of human monocytes with LPS does not lead to secretion of detectable amounts of ET-1. These results suggest a role of ET-1 as an important player in human DC biology and innate immunity in general.

Hypoxia inducible factor-1 alpha induction by tumour necrosis factor-alpha, but not by toll-like receptor agonists, modulates cellular respiration in cultured human hepatocytes

BACKGROUND/AIMS: Genes encoding for some of the mitochondrial proteins are under the control of the transcriptional factor hypoxia inducible factor-1 alpha (HIF-1 alpha), which can accumulate under normoxic conditions in inflammatory states. The aim of this study was to evaluate the effects of cobalt chloride (CoCl(2), a hypoxia mimicking agent), tumour necrosis factor-alpha (TNF-alpha) and toll-like receptor (TLR) -2, -3 and -4 agonists on HIF-1 alpha accumulation, and further on HIF-1 alpha-mediated modulation of mitochondrial respiration in cultured human hepatocytes. METHODS: The human hepatoma cell line HepG2 was used in this study. Cells were treated with CoCl(2), TNF-alpha and TLR-2, -3 and -4 agonists. HIF-1 alpha was determined by Western blotting and mitochondrial respiration in stimulated cells by high-resolution respirometry. RESULTS: CoCl(2), TNF-alpha and TLR agonists induced the expression of HIF-1 alpha in a time-dependent fashion. TNF-alpha and CoCl(2), but not TLR agonists, induced a reduction in complex I-, II- and IV-dependent mitochondrial oxygen consumption. TNF-alpha-associated reduction of cellular oxygen consumption was abolished through inhibition of HIF-1 alpha activity by chetomin (CTM). Pretreatment with cyclosporine A prevented CoCl(2)-induced reduction of complex I- and II-dependent mitochondrial oxygen consumption and TNF-alpha-induced reduction of complex-I-dependent respiration, implicating the involvement of the mitochondrial permeability transition pore openings. TNF-alpha and TLR-2, -3 and -4 agonists induced the expression of vascular endothelial growth factor, which was partially abolished by the blockage of HIF-1 alpha with CTM. CONCLUSIONS: The data suggest that HIF-1 alpha modulates mitochondrial respiration during CoCl(2) and TNF-alpha stimulation, whereas it has no effect when induced with TLR-2, -3 and -4 agonists.