ccl19 and ccl21 affect cell movements and differentiation in early Xenopus development

We characterized Xenopus laevis C-C motif chemokine ligand 19.L (ccl19.L) and C-C motif chemokine ligand 21.L (ccl21.L) during early Xenopus embryogenesis. The temporal and spatial expression patterns of ccl19.L and ccl21.L tended to show an inverse correlation, except that the expression level was higher in the dorsal side at the gastrula stage. For example, even at the dorsal sector of the gastrulae, ccl19.L was expressed in the axial region and ccl21.L was expressed in the paraxial region. Dorsal overexpression of ccl19.L and ccl21.L and knockdown of Ccl19.L and Ccl21.L inhibited gastrulation, but their functions were different in cell behaviors during morphogenesis. Observation of Keller sandwich explants revealed that overexpression of both ccl19.L and ccl21.L and knockdown of Ccl21.L inhibited the convergent extension movements, while knockdown of Ccl19.L did not. ccl19.L-overexpressing explants attracted cells at a distance and ccl21.L-overexpressing explants attracted neighboring cells. Ventral overexpression of ccl19.L and ccl21.L induced secondary axis-like structures and chrd.1 expression at the ventral side. Upregulation of chrd.1 was induced by ligand mRNAs through ccr7.S. Knockdown of Ccl19.L and Ccl21.L inhibited gastrulation and downregulated chrd.1 expression at the dorsal side. The collective findings indicate that ccl19.L and ccl21.L might play important roles in morphogenesis and dorsal-ventral patterning during early embryogenesis in Xenopus.

Increased number and altered phenotype of lymphatic vessels in peripheral lung compartments of patients with COPD

BACKGROUND

De novo lymphatic vessel formation has recently been observed in lungs of patients with moderate chronic obstructive pulmonary disease (COPD). However, the distribution of lymphatic vessel changes among the anatomical compartments of diseased lungs is unknown. Furthermore, information regarding the nature of lymphatic vessel alterations across different stages of COPD is missing. This study performs a detailed morphometric characterization of lymphatic vessels in major peripheral lung compartments of patients with different severities of COPD and investigates the lymphatic expression of molecules involved in immune cell trafficking.

METHODS

Peripheral lung resection samples obtained from patients with mild (GOLD stage I), moderate-severe (GOLD stage II-III), and very severe (GOLD stage IV) COPD were investigated for podoplanin-immunopositive lymphatic vessels in distinct peripheral lung compartments: bronchioles, pulmonary blood vessels and alveolar walls. Control subjects with normal lung function were divided into never smokers and smokers. Lymphatics were analysed by multiple morphological parameters, as well as for their expression of CCL21 and the chemokine scavenger receptor D6.

RESULTS

The number of lymphatics increased by 133% in the alveolar parenchyma in patients with advanced COPD compared with never-smoking controls (p < 0.05). In patchy fibrotic lesions the number of alveolar lymphatics increased 20-fold from non-fibrotic parenchyma in the same COPD patients. The absolute number of lymphatics per bronchiole and artery was increased in advanced COPD, but numbers were not different after normalization to tissue area. Increased numbers of CCL21- and D6-positive lymphatics were observed in the alveolar parenchyma in advanced COPD compared with controls (p < 0.01). Lymphatic vessels also displayed increased mean levels of immunoreactivity for CCL21 in the wall of bronchioles (p < 0.01) and bronchiole-associated arteries (p < 0.05), as well as the alveolar parenchyma (p < 0.001) in patients with advanced COPD compared with never-smoking controls. A similar increase in lymphatic D6 immunoreactivity was observed in bronchioles (p < 0.05) and alveolar parenchyma (p < 0.01).

CONCLUSIONS

This study shows that severe stages of COPD is associated with increased numbers of alveolar lymphatic vessels and a change in lymphatic vessel phenotype in major peripheral lung compartments. This novel histopathological feature is suggested to have important implications for distal lung immune cell traffic in advanced COPD.

Transmural flow modulates cell and fluid transport functions of lymphatic endothelium

RATIONALE

Lymphatic transport of peripheral interstitial fluid and dendritic cells (DCs) is important for both adaptive immunity and maintenance of tolerance to self-antigens. Lymphatic drainage can change rapidly and dramatically on tissue injury or inflammation, and therefore increased fluid flow may serve as an important early cue for inflammation; however, the effects of transmural flow on lymphatic function are unknown.

OBJECTIVE

Here we tested the hypothesis that lymph drainage regulates the fluid and cell transport functions of lymphatic endothelium.

METHODS AND RESULTS

Using in vitro and in vivo models, we demonstrated that lymphatic endothelium is sensitive to low levels of transmural flow. Basal-to-luminal flow (0.1 and 1 mum/sec) increased lymphatic permeability, dextran transport, and aquaporin-2 expression, as well as DC transmigration into lymphatics. The latter was associated with increased lymphatic expression of the DC homing chemokine CCL21 and the adhesion molecules intercellular adhesion molecule-1 and E-selectin. In addition, transmural flow induced delocalization and downregulation of vascular endothelial cadherin and PECAM-1 (platelet/endothelial cell adhesion molecule-1). Flow-enhanced DC transmigration could be reversed by blocking CCR7, intercellular adhesion molecule-1, or E-selectin. In an experimental model of lymphedema, where lymphatic drainage is greatly reduced or absent, lymphatic endothelial expression of CCL21 was nearly absent.

CONCLUSIONS

These findings introduce transmural flow as an important regulator of lymphatic endothelial function and suggest that flow might serve as an early inflammatory signal for lymphatics, causing them to regulate transport functions to facilitate the delivery of soluble antigens and DCs to lymph nodes.

Salmonella typhimurium engineered to produce CCL21 inhibit tumor growth

Intravenously-applied bacteria tend to accumulate in tumors and can sporadically lead to tumor regression. Systemic administration of attenuated Salmonella typhimurium is safe and has shown no significant adverse effects in humans. The purpose of this study was to test the hypothesis that engineering S. typhimurium to express a chemokine, CCL21, would increase anti-tumor activity. We engineered an attenuated strain of S. typhimurium to produce the chemokine CCL21. Attenuated S. typhimurium expressing CCL21 significantly inhibited the growth of primary tumors and pulmonary metastases in preclinical models of multi-drug-resistant murine carcinomas, while control bacteria did not. Histological analysis of tumors showed marked inflammatory cell infiltrates in mice treated with CCL21-expressing but not control bacteria. Levels of cytokines and chemokines known to be induced by CCL21 [e.g., interferon-gamma (INFgamma), CXCL9, and CXCL10] were significantly elevated in tumors of mice treated with CCL21-expressing but not control S. typhimurium. The anti-tumor activity was found to be dependent on CD4- and CD8-expressing cells, based on antibody-mediated in vivo immuno-depletion experiments. Anti-tumor activity was achieved without evidence of toxicity. In summary, chemokine-expressing, attenuated bacteria may provide a novel approach to cancer immunotherapy for effective and well-tolerated in vivo delivery of immunomodulatory proteins.

Modulation of thalamic nociceptive processing after spinal cord injury through remote activation of thalamic microglia by cysteine cysteine chemokine ligand 21

Spinal cord injury (SCI) results in the generation and amplification of pain caused in part by injury-induced changes in neuronal excitability at multiple levels along the sensory neuraxis. We have previously shown that activated microglia, through an ERK (extracellular signal-regulated kinase)-regulated PGE(2) (prostaglandin E(2)) signaling mechanism, maintain neuronal hyperexcitability in the lumbar dorsal horn. Here, we examined whether microglial cells in the thalamus contribute to the modulation of chronic pain after SCI, and whether microglial activation is governed by spinally mediated increases in the microglial activator cysteine-cysteine chemokine ligand 21 (CCL21). We report that CCL21 is upregulated in dorsal horn neurons, that tissue levels are increased in the dorsal horn and ventral posterolateral (VPL) nucleus of the thalamus 4 weeks after SCI, and that the increase can be differentially reduced by spinal blockade at T1 or L1. In intact animals, electrical stimulation of the spinothalamic tract induces increases in thalamic CCL21 levels. Recombinant CCL21 injected into the VPL of intact animals transiently activates microglia and induces pain-related behaviors, effects that could be blocked with minocycline. After SCI, intra-VPL antibody-mediated neutralization of CCL21 decreases microglial activation and evoked hyperexcitability of VPL neurons, and restores nociceptive thresholds to near-normal levels. These data identify a novel pathway by which SCI triggers upregulation of the neuroimmune modulator CCL21 in the thalamus, which induces microglial activation in association with pain phenomena.

Lymphotoxin beta receptor signaling is required for inflammatory lymphangiogenesis in the thyroid

Infiltration of lymphocytes into the thyroid gland and formation of lymph node-like structures is a hallmark of Hashimoto's thyroiditis. Here we demonstrate that lymphatic vessels are present within these infiltrates. Mice overexpressing the chemokine CCL21 in the thyroid (TGCCL21 mice) developed similar lymphoid infiltrates and lymphatic vessels. TGCCL21 mice lacking mature T and B cells (RAGTGCCL21 mice) did not have cellular infiltrates or increased number of lymphatic vessels compared with controls. Transfer of CD3(+)CD4(+) T cells into RAGTGCCL21 mice promoted the development of LYVE-1(+)podoplanin(+)Prox-1(+) vessels in the thyroid. Genetic deletion of lymphotoxin beta receptor or lymphotoxin alpha abrogated development of lymphatic vessels in the inflamed areas in the thyroid but did not affect development of neighboring lymphatics. These results define a model for the study of inflammatory lymphangiogenesis in the thyroid and implicate lymphotoxin beta receptor signaling in this process.

Regulation of dendritic cell migration to the draining lymph node: impact on T lymphocyte traffic and priming

Antigen-pulsed dendritic cells (DCs) are used as natural adjuvants for vaccination, but the factors that influence the efficacy of this treatment are poorly understood. We investigated the parameters that affect the migration of subcutaneously injected mouse-mature DCs to the draining lymph node. We found that the efficiency of DC migration varied with the number of injected DCs and that CCR7+/+ DCs migrating to the draining lymph node, but not CCR7-/- DCs that failed to do so, efficiently induced a rapid increase in lymph node cellularity, which was observed before the onset of T cell proliferation. We also report that DC migration could be increased up to 10-fold by preinjection of inflammatory cytokines that increased the expression of the CCR7 ligand CCL21 in lymphatic endothelial cells. The magnitude and quality of CD4+ T cell response was proportional to the number of antigen-carrying DCs that reached the lymph node and could be boosted up to 40-fold by preinjection of tumor necrosis factor that conditioned the tissue for increased DC migration. These results indicate that DC number and tissue inflammation are critical parameters for DC-based vaccination.