Contrast-Enhanced Ultrasound Reveals Partial Perfusion Recovery After Hindlimb Ischemia as Opposed to Full Recovery by Laser Doppler Perfusion Imaging.

Mouse models are critical in developing new therapeutic approaches to treat peripheral arterial disease (PAD). Despite decades of research and numerous clinical trials, the efficacy of available therapies is limited. This may suggest shortcomings in our current animal models and/or methods of assessment. We evaluated perfusion measurement methods in a mouse model of PAD by comparing laser Doppler perfusion imaging (LDPI, the most common technique), contrast-enhanced ultrasound (CEUS, an emerging technique) and fluorescent microspheres (conventional standard). Mice undergoing a femoral artery ligation were assessed by LDPI and CEUS at baseline and 1, 4, 7, 14, 28, 60, 90 and 150 d post-surgery to evaluate perfusion recovery in the ischemic hindlimb. Fourteen days after surgery, additional mice were measured with fluorescent microspheres, LDPI, and CEUS. LDPI and CEUS resulted in broadly similar trends of perfusion recovery until 7 d post-surgery. However, by day 14, LDPI indicated full recovery of perfusion, whereas CEUS indicated ∼50% recovery, which failed to improve even after 5 mo. In agreement with the CEUS results, fluorescent microspheres at day 14 post-surgery confirmed that perfusion recovery was incomplete. Histopathology and photoacoustic microscopy provided further evidence of sustained vascular abnormalities.

Evaluation of pharmacokinetic and pharmacodynamic profiles of liposomes for the cell type-specific delivery of small molecule drugs.

Liposome-based drug formulations represent an exciting avenue of research as they increase efficacy to toxicity ratios. Current formulations rely on passive accumulation to the disease site where drug is taken up by the cells. Ligand mediated targeting increases the net accumulation of liposomes, however, an unexplored benefit is to potentially refine pharmacodynamics (PD) of a drug specifically to different cell types within diseased tissue. As a model system, we engineered cardiomyocyte- (I-1) and endothelial-targeted (B-40) liposomes to carry a VEGFR2 inhibitor (PTK787), and examined the effect of cell type-specific delivery on both pharmacokinetics (PK) and PD. Neovascularization in post-myocardial infarction was significantly reduced by B-40 liposomes loaded with PTK787 as compared to animals injected with I-1 liposomes, and profoundly more as compared to free PTK787. This study thus shows that the intraorgan targeting of drugs through cell type-specific delivery holds substantial promise towards lowering the minimal efficacious dose administered systemically.

Heterogeneity of lung mononuclear phagocytes during pneumonia: contribution of chemokine receptors.

Bacterial pneumonia is a common and dangerous illness. Mononuclear phagocytes, which comprise monocyte, resident and recruited macrophage, and dendritic cell subsets, are critical to antimicrobial defenses, but the dynamics of their recruitment to the lungs in pneumonia is not established. We hypothesized that chemokine-mediated traffic of mononuclear phagocytes is important in defense against bacterial pneumonia. In a mouse model of Klebsiella pneumonia, circulating Ly6C(hi) and, to a lesser extent, Ly6C(lo) monocytes expanded in parallel with accumulation of inflammatory macrophages and CD11b(hi) dendritic cells and plasmacytoid dendritic cells in the lungs, whereas numbers of alveolar macrophages remained constant. CCR2 was expressed by Ly6C(hi) monocytes, recruited macrophages, and airway dendritic cells; CCR6 was prominently expressed by airway dendritic cells; and CX3CR1 was ubiquitously expressed by blood monocytes and lung CD11b(hi) dendritic cells during infection. CCR2-deficient, but not CCL2-, CX3CR1-, or CCR6-deficient animals exhibited worse outcomes of infection. The absence of CCR2 had no detectable effect on neutrophils but resulted in reduction of all subsets of lung mononuclear phagocytes in the lungs, including alveolar macrophages and airway and plasmacytoid dendritic cells. In addition, absence of CCR2 skewed the phenotype of lung mononuclear phagocytes, abrogating the appearance of M1 macrophages and TNF-producing dendritic cells in the lungs. Taken together, these data define the dynamics of mononuclear phagocytes during pneumonia.

P-selectin-mediated platelet-neutrophil aggregate formation activates neutrophils in mouse and human sickle cell disease.

OBJECTIVE: To determine the role of platelets in stimulating mouse and human neutrophil activation and pulmonary injury in sickle cell disease (SCD). METHODS AND RESULTS: Both platelet and neutrophil activation occur in SCD, but the interdependence of these events is unknown. Platelet activation and binding to leukocytes were measured in mice and patients with SCD and in controls. Relative to controls, blood obtained from mice or patients with SCD contained significantly elevated platelet-neutrophil aggregates (PNAs). Both platelets and neutrophils found in sickle PNAs were activated. Multispectral imaging (ImageStream) and conventional flow cytometry revealed a subpopulation of activated neutrophils with multiple adhered platelets that expressed significantly more CD11b and exhibited greater oxidative activity than single neutrophils. On average, wild-type and sickle PNAs contained 1.1 and 2.6 platelets per neutrophil, respectively. Hypoxia/reoxygenation induced a further increase in PNAs in mice with SCD and additional activation of both platelets and neutrophils. The pretreatment of mice with SCD with clopidogrel or P-selectin antibody reduced the formation of PNAs and neutrophil activation and decreased lung vascular permeability. CONCLUSIONS: Our findings suggest that platelet binding activates neutrophils and contributes to a chronic inflammatory state and pulmonary dysfunction in SCD. The inhibition of platelet activation may be useful to decrease tissue injury in SCD, particularly during the early stages of vaso-occlusive crises.

A nephritogenic peptide induces intermolecular epitope spreading on collagen IV in experimental autoimmune glomerulonephritis.

This group previously identified a peptide p13 of alpha3(IV)NC1 domain of type IV collagen that induces experimental autoimmune glomerulonephritis (EAG) in rats with generation of antibodies to sites on alpha3(IV)NC1 external to the peptide as a result of intramolecular epitope spreading. It was hypothesized that intermolecular epitope spreading to other collagen IV chains also was induced. Rats were immunized with nephritogenic peptide that was derived from the amino terminal part of rat alpha3(IV)NC1 domain, and serum and kidney eluate were examined for antibodies to both native and recombinant NC1 domains of collagen IV. Peptide induced EAG with proteinuria and decreased renal function and glomerular basement membrane IgG deposits. Sera from these rats were examined by ELISA, which revealed reactivity not only to immunizing peptide but also to human and rat alpha3(IV)NC1 and to human alpha4(IV)NC1 domains. Kidney eluate that was depleted of alpha3(IV)NC1 antibodies still reacted to alpha4(IV)NC1, and alpha3(IV)NC1 column-bound antibody reacted with alpha3(IV)NC1. There was minimal reactivity to other collagen chains. Eluate that was adsorbed to NC1 hexamer from rat glomerular basement membrane lost all reactivity to glomerular constituents, and the eluted antibodies reacted to alpha3(IV)NC1 and alpha4(IV)NC1 domains. These studies show that a T cell epitope of alpha3(IV)NC1 induces EAG, intramolecular epitope spreading along alpha3(IV)NC1, and intermolecular epitope spreading to alpha4(IV)NC1 domain with minimal or no reactivity to other collagen chains or glomerular constituents. This is the first demonstration in EAG of intermolecular epitope spreading and identification of the spread epitopes.

Epitope spreading and autoimmune glomerulonephritis in rats induced by a T cell epitope of Goodpasture's antigen.

An amino-terminal region of alpha3 chain of type IV collagen noncollagenous domain [alpha3(IV)NC1] that induces experimental autoimmune glomerulonephritis (EAG) in rats has been identified. Only recombinant antigens that contain a nine-amino acid (AA) span of alpha3(IV)NC1, consistent with a T cell epitope, could induce EAG. It was hypothesized that synthetic peptides of this region should induce EAG. Human and rat peptides of this region were synthesized and rats were immunized to define the nephritogenic epitope. A 13-AA rat peptide induced EAG with proteinuria, decreased renal function, and glomerular basement membrane (GBM)-bound deposits in half of the rats. This peptide induces lymph node cell proliferation and development of antibodies to epitopes of alpha3(IV)NC1 external to the peptide immunogen. Carboxy-terminal extension to 21 amino acids results in all rats' demonstrating anti-GBM antibody and severe EAG. Asparagine at position 19 is critical for EAG induction. None of the 50 rats that were immunized with peptide that contained human sequence with isoleucine at position 19 developed EAG, whereas rat sequence with asparagine 19 induced EAG. Truncation of amino terminal AA of the peptide aborts EAG induction. These studies demonstrate that a T cell epitope of alpha3(IV)NC1 induces lymph node cell proliferation, EAG, and intramolecular epitope spreading; that the length of this peptide influences the formation of anti-GBM antibody; and that the presence of asparagine at position 19 of the peptide is critical to disease induction.

Molecular mapping of the Goodpasture's epitope for glomerulonephritis.

Goodpasture's syndrome is an autoimmune disease characterized by pulmonary hemorrhage, glomerulonephritis, and antiglomerular basement membrane (GBM) antibodies. We have studied a rat model with chimeric proteins (CPs) consisting of portions of the nephritogenic non-collagenous domain of alpha3 type IV collagen (alpha3(IV)NC1) and non-nephritogenic alpha1(IV)NC1. CPs with aminoterminal alpha3 that contains the major epitope for Goodpasture antibody binding induced EAG. We next immunized with D3, an alpha1(IV)NC1 CP with 69AA of alpha3(IV)NC1 (binds Goodpasture sera), D4, the D3 construct shortened by 4 AA (nonbinding), P9 and P10, single AA mutants (nonbinding) and S2, an alpha1(IV)NC1 with nine AA of alpha3(IV)NC1 (binding). GBM, S2 and D3 induced EAG. GBM immunized rats had intense IgG deposits but S2 and D3 rats had minimal deposits. A 13 mer rat peptide encompassing the aminoterminal site induced EAG sans antibody, while peptides not encompassing the region failed to induce GN. Asparagine at position 19 rather than isoleucine was essential for disease induction. These studies define critical limited AA sequences of alpha3(IV)NC1 associated with glomerulonephritis without antibody, and demonstrate that this region contains a T-cell epitope responsible for induction of glomerulonephritis.

Immunodominant epitopes of alpha3(IV)NC1 induce autoimmune glomerulonephritis in rats.

BACKGROUND: The major Goodpasture antibody binding epitopes have been localized to the amino-terminal third of the noncollagenous domain (NC1) of the alpha3 chain of type IV collagen [alpha3(IV)NC1]. The present study determined whether the same epitopes induce glomerulonephritis in rats. METHODS: We immunized Wistar Kyoto (WKY) rats with human alpha3(IV)/alpha1(IV)NC1 chimeric proteins or full-length recombinant alpha3(IV)NC1 (alpha3732). Chimeric protein constructs were thirds of alpha3(IV)NC1 (CP333) replaced by corresponding sequences of homologous nonreactive alpha1(IV)NC1 (CP111). All chimeric proteins contained 30 amino acids of type X collagen at the amino terminus except alpha3732. Two other constructs, T195 EA (EA) and T194 EB (EB), were entirely alpha1(IV)NC1, except for antibody-immunodominant amino acids from the first and second thirds of alpha3(IV)NC1. RESULTS: Construct immunized animals developed specific antibody responses to recombinant proteins and native human, bovine and rat NC1. CP311 immunized rats, as well as alpha3732 rats, had glomerular IgG, fibrin, and glomerulonephritis with proteinuria by 3 weeks. CP331 produced more severe disease, comparable to positive controls. CP111 produced no disease. EA, but not EB, induced severe glomerulonephritis. Half-dose each of EA plus EB induced disease identical to full-dose EA alone. CONCLUSION: The amino third of alpha3(IV)NC1 which contains the major epitope for Goodpasture antibody binding, also induces glomerulonephritis in rats. The middle third of alpha3(IV)NC1 does not induce glomerulonephritis but appears to enhance disease with the amino terminal third. Finally, the presence of the collagen X leader sequence appears to convey greater nephritogenicity. These studies suggest that not only the nephritogenic epitope itself, but flanking sequences and the conformational context of the nephritogenic epitope may influence its ability to cause glomerulonephritis.

Point mutations of single amino acids abolish ability of alpha3 NC1 domain to elicit experimental autoimmune glomerulonephritis in rats.

We previously showed concordance between Goodpasture syndrome antibody binding and production of experimental glomerulonephritis using human chimeric proteins. We now examine a more limited amino-terminal region of alpha3(IV) non-collagenous domain (NC1) and the impact of single amino acid (AA) mutations of this region on glomerulonephritis induction. Rats were immunized with collagenase-solubilized glomerular basement membrane (csGBM), D3, an alpha1(IV)NC1 chimeric protein with 69 AA of alpha3(IV)NC1 (binds Goodpasture sera), D4, the D3 construct shortened by 4 AA (non-binding), P9, P10, single AA mutants (non-binding), and S2, alpha1(IV)NC1 with 9 AA of alpha3(IV)NC1 (binding). All rats immunized with csGBM and S2 and 50% of D3 rats developed glomerulonephritis. csGBM rats had intense GBM-bound IgG deposits, but S2 and D3 rats had minimal deposits. None of the D4, P9, or P10 rats developed glomerulonephritis. Lymphocytes from nephritic rats proliferated with csGBM, S2, and D3, but not with D4, P9, or P10. Discrete segments of alpha3(IV)NC1 within the alpha1(IV)NC1 backbone can induce glomerulonephritis. Single AA mutations within that epitope render the antigen unresponsive to Goodpasture sera and incapable of inducing glomerulonephritis. These studies support the concordance of glomerulonephritis inductivity and Goodpasture serum binding. Further, they define a critical limited AA sequence within alpha3(IV)NC1 of nine or fewer AA, which confers nephritogenicity to the nonnephritogenic alpha1(IV)NC1 without in vivo antibody binding. This region may be a T-cell epitope responsible for induction of glomerulonephritis in this model in rats and Goodpasture syndrome in man.

Synthetic peptides of Goodpasture's antigen in antiglomerular basement membrane nephritis in rats.

Goodpasture's syndrome (GPS) is an autoimmune disease characterized by pulmonary hemorrhage, glomerulonephritis and anti-glomerular basement membrane (GBM) antibodies. The alpha(3) noncollagenous domain (NC1) of type IV collagen [alpha(3)(IV)] is the pathogen. The disease is T-cell-dependent; thus linear peptides initiate the autoimmune process. Studies in a rat model of GPS, experimental autoimmune glomerulonephritis (EAG), have shown that the carboxy-terminal 36 amino acids (purportedly the pathogenic epitope) are not responsible for disease induction. More recent studies implicate the amino terminus of alpha(3)(IV)NC1. Finding the nephritogenic epitope(s) is crucial in the understanding of the disease and for treatment. Because alpha(3)(IV)NC1 contains the antigens that induce GN in rats and human beings, we hypothesized that regions of the alpha(3)(IV)NC1 other than the carboxy terminus were responsible for disease. We investigated overlapping peptides spanning the entire NC1 domain of the alpha(3)(IV) chain N-terminal to the 36-mer (Goodpasture epitope) using the EAG rat model. Most peptides elicited antibody responses exclusively to themselves but not to native GBM. T-cells from GBM-immunized rats proliferated in vitro after stimulation with peptides 6, 8, 14, and 15, 24-mer and 23-mer. Fifteen percent of peptide 8 and peptide 14 rats had mild glomerulonephritis. In none of the animals immunized with other peptides did glomerulonephritis develop. These data suggest that conformation-dependent sites, posttranslational modification, multiple epitopes, concomitant antibody formation, or other disturbances are important in the ability of alpha(3)(IV)NC1 to induce EAG in rats and may also be important in the induction of GPS in human beings.