Complement Anaphylatoxin C5a-Induced Mouse Lymphatic Functions Modulate Interactions Between Endothelial Cells and T Lymphocytes.

The vascular endothelium has been discovered in the past several years to be important in shaping the cellular immune response. During the immune response the vascular endothelium is constantly perturbed by biologically potent molecules, including the complement activation peptides, C3a and C5a. Despite the importance of C3a and C5a in inflammation and immunity, their role in modulating lymphocyte function via activation of vascular endothelial cells is unknown. Accordingly, we investigated the regulated expression of the C3a and C5a receptors (complement anaphylatoxin C3a receptor [C3aR] and complement anaphylatoxin C5a receptor 1 [C5aR1]) on human umbilical vascular endothelial cells (HUVECs) and examined how C3a or C5a activation of HUVECs affects the activation and polarization of lymphatic cells. Our findings demonstrated that C3a and C5a increase C3aR and C5aR1 expression by HUVECs as well as directing their cellular transmigration and spreading through transwell filters. Moreover, C3a- or C5a-stimulated endothelial cells: (1) caused activation of B-lymphoblasts with significant increase in Fas Ligand (CD95L) (FasL), CD69, and IL-R1 expression, and (2) skewed T-lymphoblast cells toward a Th1 subtype, (CD4+ /CCR5+ ) that correlated with significant increase of IFN-γ. Collectively, these data indicate that C3a and C5a signaling is important in the activation and polarization of lymphocytes as they traffic through the vascular endothelium during the immune response.

Our knowledge on lymphatic vessel function is lagging that of blood vessels. Baranwal et al.1 help bridge this gap in the present issue of Acta Physiologica, by exploring caveolae in lymphatic function. As models, they use mice constitutively lacking caveolin-1 (Cav-1), the primary protein in caveolae required for their formation in endothelial cells and lymphatic endothelial cell (LEC) with specific caveolin-1 gene deletion. In mammals, there are two circulatory systems, the blood vessels that form a closed circulatory system and the lymphatic vessels, where the latter constitutes a one-way conduit returning filtered interstitial fluid and leukocytes via lymph nodes back to the blood circulation. The lymphatic system thus contributes to fluid balance preservation, absorption of digested fat via intestinal lymphatics and immunosurveillance. Formation of lymph starts as interstitial fluid enters initial lymphatics via paracellular transport facilitated by overlapping button-like junctions that allow passive entry of fluid and macromolecules2 . From its origin lymph is transported centrally via collecting vessels having unidirectional valves and smooth muscle with intrinsic contractility, thus, facilitating unidirectional transport3 .

The complement anaphylatoxins C3a and C5a are critical effectors of innate immunity. Beyond this role, emerging evidence has implicated them in cancer progression. However, their specific functions in non-small cell lung cancer (NSCLC) have not been systematically reviewed. This review aimedto synthesize the evidence on the contribution of C3a and C5a to NSCLC progression and their potential as therapeutic targets. This systematic review followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A comprehensive search of PubMed, Scopus, and Cochrane Librarywasperformed up to May 2025. The PICO (Population, Intervention, Comparison, Outcome)framework guided the inclusion of studies involving NSCLC patients or human cell lines, reporting on C3a/C5a levels and their association with clinical outcomes or pro-tumoral effects. The risk of biaswasassessed using the OHAT tool.From 11,838 initially identified records, six studies met the inclusion criteria based on PICO criteria requiring direct investigation of C3a/C5a in human NSCLC contexts.The evidence strongly and consistently points to a critical pro-tumoral role for theC5a/C5aR1 axis. Key findings include: C5a promotes NSCLC cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition; high C5aR1 expression is an independent prognostic factor for worse recurrence-free survival; and tumor-derived C5a enhances angiogenesis and metastatic potential, particularly to bone. NSCLC cells evade complement attack by producing regulators like Factor H. In contrast, the role of C3a was less defined. While C5a was consistently elevated and active in the tumor microenvironment, one study noted a local decrease of C3a in tumor tissues, suggesting a potentially different or context-dependent function.Risk of bias assessment using the OHAT tool indicated low to moderate risk across the included studies. This systematic review shows that complement anaphylatoxins, especially C5a, drive NSCLC progression by promoting a pro-tumoral microenvironment and metastasis. Targeting the C5a/C5aR1 axis is a promising therapeutic strategy, though more research is needed.

Cardiac healing, which follows myocardial infarction, is a complex process guided by intricate interactions among different components. Some resident cell populations with a potential role in cardiac healing have already been described in cardiac tissues. These non-cardiomyocyte cell subsets, globally described as cardiac pluripotent/progenitor cells (CPCs), are able to differentiate into all three major cardiac cell lineages (endothelial, smooth muscle and cardiomyocyte cells) in experimental settings. Nevertheless, physiological cardiac healing results in a fibrous scar, which remains to be fully modelled experimentally. Since a role for complement anaphylatoxins (C3a and C5a) has been described in several regeneration/repair processes, we examined the effects that C3a and C5a exert on a defined population of CPCs. We found that C3a and C5a are able to enhance CPC migration and proliferation. In vitro studies showed that this effect is linked to activation of telomerase mRNA and partial preservation of telomere length, in an NFκB-dependent manner. In addition, anaphylatoxin signalling modulates the CPC phenotype, increasing myofibroblast differentiation and reducing endothelial and cardiac gene expression. These findings may denote that C3a and C5a are able to maintain/increase the cardiac stem cell pool within the heart, whilst simultaneously facilitating and modulating resident cell differentiation. We found that this modulation was directed towards scar forming cells, which increased fibroblast/myofibroblast generation and suggests that both these anaphylatoxins could play a relevant role in the damage-coupled activation of resident cells, and regulation of the cardiac healing process after injury.

Lymphatic vessels exist in nearly all tissues, yet, despite their omnipresence, there remains a large knowledge gap between the described fundamental roles of lymphatic capillaries and our understanding of their functional biology, adaptive ability, and pathological response. This thesis addressed these shortcomings by utilizing an integrative biomedical engineering approach to examine molecular and mechanical regulators of lymphatic capillaries using in vivo models of lymphatic capillary biology, function, and adaptation. Using a model of skin regeneration in the mouse tail, we demonstrated that slow interstitial flow created by lymphatic drainage was necessary for lymphatic capillary organization. This novel model permitted the identification of spatial, temporal and chemical factors governing lymphangiogenesis. In contrast to the sprouting mechanism of blood angiogenesis, lymphatic endothelial cells (LECs) were demonstrated to organize in a vasculogenesis-like manner, migrating in the direction of interstitial flow and then organizing into functional lymphatic capillaries. Lymphangiogenesis was inhibited by blocking vascular endothelial growth factor (VEGF)-C signaling from day 0, but initiation of receptor blockade once LECs had already migrated did not prevent vessel organization. This uniquely demonstrated the need for a biochemical mediator (VEGF-C) to initiate lymphangiogenesis, but that an important biomechanical force, interstitial flow, was necessary for functional capillary organization. Further insight into the necessity of interstitial flow in LEC biology was found in the response of lymphatic capillary to induced lymphedema, wherein lymphatic drainage is significantly reduced. In a mouse tail model of secondary lymphedema, we demonstrated that the edematous environment – characterized by extracellular matrix breakdown, lipid accumulation, and reduced interstitial flow – resulted in hyperplasia of LECs but concurrent poor function due to the lack of interstitial flow as an organizational guiding cue. Similar dermal matrix adaptations to dysfunctional lymphatic drainage were also noted in two mouse models of congenital lymphedema, the Chy and VEGFR-3-Ig mice, further demonstrating the intimate connection of lymphatic capillary function with tissue maintenance and remodeling. To quantitatively demonstrate the changes in lymphatic capillary uptake and tissue hydraulic conductivity found in these and other transgenic mouse models, we developed a poroelastic model of interstitial transport. Tissue hydraulic conductivity was also calculated in tissues lacking lymphatics using an unsteady-state solution, demonstrating that lymphedema causes a significant increase in tissue conductivity. This model was then utilized to assess the effects of a high fat diet, metabolic disorders, and lymphatic dysfunction on the tissue and on lymphatic capillary function. We discovered that lymphatic capillary uptake function was significantly reduced with dyslipidemia, suggesting a novel interplay between lymphatic function and lipid metabolism. Additionally, we uncovered a new and critical role for lymphangiogenesis and lymphatic transport in reproduction. We demonstrated that lymphangiogenesis is a regular, non-pathological event during folliculogenesis in the ovary. These new lymphatic capillaries are seemingly necessary for hormone transport from the ovary – an essential feedback mechanism during pregnancy. Blockade of lymphangiogenesis resulted in decreased systemic progesterone and estradiol levels and resulted in failed fetal development. In conclusion, this work highlights the critical roles of the lymphatic circulation and demonstrates the interplay between lymphatic biology and the biochemical and biophysical environment in which lymphatic capillaries reside. Interstitial flow and the interstitium modulate lymphatic behavior, and lymphatic function, in turn, controls the tissue microenvironment.

Beyond PROX1: transcriptional, epigenetic, and noncoding RNA regulation of lymphatic identity and function.

Iron deficiency is frequent in patients with chronic inflammatory conditions (e.g., chronic heart failure, chronic kidney disease, cancers, and bowel inflammatory diseases). Indeed, high concentrations of inflammatory cytokines increase hepcidin concentrations that lead to the sequestration of iron in cells of the reticuloendothelial system (functional iron deficiency). Iron parameters are often assessed only in the context of anemia, but iron deficiency, even without anemia, is present in about half of patients with inflammatory conditions. Iron deficiency worsens underlying chronic diseases and is an independent factor of morbidity and mortality. In daily practice, the most effective biomarkers of iron status are serum ferritin, which reflects iron storage, and transferrin saturation, which reflects the transport of iron. Serum ferritin is increased in an inflammatory context, and there is still no consensus on the threshold to be used in chronic inflammatory conditions. Nevertheless, recent recommendations of international guidelines agreed to define iron deficiency by serum ferritin <100 µg/L and/or transferrin saturation <20%. Iron parameters remain, however, insufficiently assessed in patients with chronic inflammatory conditions. Indeed, clinical symptoms of iron deficiency, such as fatigue, are not specific and often confused with those of the primary disease. Iron repletion, preferably by the intravenous route to bypass tissue sequestration, improves clinical signs and quality of life. Because of the negative impact of iron deficiency on chronic inflammatory diseases and the efficacy of intravenous iron repletion, screening of iron parameters should be part of the routine examination of all patients with chronic inflammatory diseases.

Key pointsObesity results in perilymphatic inflammation and lymphatic dysfunction.Lymphatic dysfunction in obesity is characterized by decreased lymphatic vessel density, decreased collecting lymphatic vessel pumping frequency, decreased lymphatic trafficking of immune cells, increased lymphatic vessel leakiness and changes in the gene expression patterns of lymphatic endothelial cells.Aerobic exercise, independent of weight loss, decreases perilymphatic inflammatory cell accumulation, improves lymphatic function and reverses pathological changes in gene expression in lymphatic endothelial cells.Although previous studies have shown that obesity markedly decreases lymphatic function, the cellular mechanisms that regulate this response remain unknown. In addition, it is unclear whether the pathological effects of obesity on the lymphatic system are reversible with behavioural modifications. The purpose of this study, therefore, was to analyse lymphatic vascular changes in obese mice and to determine whether these pathological effects are reversible with aerobic exercise. We randomized obese mice to either aerobic exercise (treadmill running for 30 min per day, 5 days a week, for 6 weeks) or a sedentary group that was not exercised and analysed lymphatic function using a variety of outcomes. We found that sedentary obese mice had markedly decreased collecting lymphatic vessel pumping capacity, decreased lymphatic vessel density, decreased lymphatic migration of immune cells, increased lymphatic vessel leakiness and decreased expression of lymphatic specific markers compared with lean mice (all P < 0.01). Aerobic exercise did not cause weight loss but markedly improved lymphatic function compared with sedentary obese mice. Exercise had a significant anti‐inflammatory effect, resulting in decreased perilymphatic accumulation of inflammatory cells and inducible nitric oxide synthase expression. In addition, exercise normalized isolated lymphatic endothelial cell gene expression of lymphatic specific genes, including VEGFR‐3 and Prox1. Taken together, our findings suggest that obesity impairs lymphatic function via multiple mechanisms and that these pathological changes can be reversed, in part, with aerobic exercise, independent of weight loss. In addition, our study shows that obesity‐induced lymphatic endothelial cell gene expression changes are reversible with behavioural modifications.

In recent years, the function of the lymphatic system in atherosclerosis has attracted attention due to its role in immune cell trafficking, cholesterol removal from the periphery, and regulation of the inflammatory response. However, knowledge of the mechanisms regulating lymphangiogenesis and lymphatic function in the pathogenesis of atherosclerosis is limited. Endothelial microparticles carrying circulating microRNA (miRNA)s are known to mediate cell–cell communication, and our previous research showed that miRNA-19b in EMPs (EMPmiR-19b) was significantly increased in circulation and atherosclerotic vessels, and this increase in EMPmiR-19b promoted atherosclerosis. The present study investigated whether atherogenic EMPmiR-19b influences pathological changes of the lymphatic system in atherosclerosis. We first verified increased miR-19b levels and loss of lymphatic system function in atherosclerotic mice. Atherogenic western diet-fed ApoE-/- mice were injected with phosphate-buffered saline, EMPs carrying control miRNA (EMPcontrol), or EMPmiR-19b intravenously. The function and distribution of the lymphatic system was assessed via confocal microscopy, Evans blue staining, and pathological analysis. The results showed that lymphatic system dysfunction existed in the early stage of atherosclerosis, and the observed pathological changes persisted at the later stage, companied by an increased microRNA-19b level. In ApoE-/- mice systemically treated with EMPmiR-19b, the distribution, transport function, and permeability of the lymphatic system were significantly inhibited. In vitro experiments showed that miRNA-19b may damage the lymphatic system by inhibiting lymphatic endothelial cell migration and tube formation, and a possible mechanism is the inhibition of transforming growth factor beta receptor type II (TGF-βRII) expression in lymphatic endothelial cells by miRNA-19b. Together, our findings demonstrate that atherogenic EMPmiR-19b may destroy lymphatic system function in atherosclerotic mice by downregulating TGF-βRII expression.

The lymphatic system provides a major route of cancer cell dissemination from the primary lesion site, to regional draining lymph nodes (LNs), through the lymphatic to blood vasculatures, and ultimately to distant sites of metastasis. However, to date there has been no in vivo imaging technique available to demonstrate functional and structural changes of overall lymphatic system in response to tumor growth and metastasis. In order to elucidate whether there are spatial and temporal changes in lymphatic function and architecture during tumor progression, we employed a dynamic near-infrared (NIR) fluorescence imaging technique. C6/Lacz rat glioma cells were implanted intradermally into the tail at 1 to 2 cm caudal to the rectum or in the right hindlimb in balb/c nude mice. Mice with a tumor in the tail were imaged at three weeks post implantation and mice with a tumor in the hindlimb at two and three weeks after tumor inoculation. Dynamic NIR imaging with 200 ms exposure time was conducted after intradermal injection of indocyanine green (ICG) to the base of the mouse tail for a hindlimb tumor model and to the tail 2cm away from the tail tip for a tail tumor model. Our imaging data in mice with a tail tumor show no uptake of fluorophore in the lymphatic capillaries in the skin above the tumor, which is in agreement with previous reports. In addition, our results show greater staining of lymphatic capillary network to the distal tumor periphery, dilated and tortuous collecting lymphatic vessels, and reduced or loss of propulsive lymphatic flow. Moreover, altered lymphatic drainage patterns and abnormal lymphatic flow from the collecting lymphatic vessel to the lymphatic capillaries at the distal tumor margin were detected. In a hindlimb tumor model, the lymphatic drainage pattern transiently changed with progressive disease. Mice with either the inguinal (primary) or axillary (secondary) LN metastasis showed dilated and leaky fluorescent lymphatic vessels, which circumvented the primary tumor and often the inguinal LN with a tumor and drained to the brachial LN. In one mouse with the inguinal and axillary LN metastases, ICG-labeled lymph drained across the midline of the animal body and thus to the left axillary LN. Magnified fluorescent images also show diffuse dye patterns. In addition, reduced lymphatic contractile function was seen in mice with LN metastasis. In summary, we showed in an animal model that gross cancer metastasis to the draining LNs is accompanied by abnormal lymphatic drainage pathway as well as reduced functional lymph propulsion in comparison to tumor-free mice. Therefore, this emerging NIR fluorescence imaging technology can be used to non-invasively and quantitatively detect functional lymphatic changes associated with cancer, which may enable accurate nodal staging of cancer patients and provide new approaches to diagnoses and therapies against cancer metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-277.

The lymphatic system and the cardiovascular (CV) system work together to maintain body fluid homeostasis. Despite that, the lymphatic system has been relatively neglected as a potential drug target and a source of adverse effects from CV drugs. Like the heart, the lymphatic vessels undergo phasic contractions to promote lymph flow against a pressure gradient. Dysfunction or failure of the lymphatic pump results in fluid imbalance and tissue oedema. While this can be due to drug effects, it is also a feature of breast cancer-associated lymphoedema, chronic venous insufficiency, congestive heart failure, and acute systemic inflammation. There are currently no specific drug treatments for lymphatic pump dysfunction in clinical use despite the wealth of data from pre-clinical studies. The aim of this study was to identify (i) drugs with direct effects on lymphatic tonic and phasic contractions with potential for clinical application, and (ii) drugs in current clinical use that have a positive or negative side effect on lymphatic function. We comprehensively reviewed all studies that tested the direct effect of a drug on the contractile function of lymphatic vessels. Of the 208 drugs identified from 193 studies, about a quarter had only stimulatory effects on lymphatic tone, contraction frequency, and/or contraction amplitude. Of Food and Drug Administration-approved drugs, there were 14 that increased lymphatic phasic contractile function. The most frequently used class of drugs with inhibitory effects on lymphatic pump function were the calcium channels blockers. This review highlights the opportunity for specific drug treatments of lymphatic dysfunction in various disease states and for avoiding adverse drug effects on lymphatic contractile function.

Inflammatory breast cancer (IBC) presents as rapid-onset swelling and breast skin changes caused by tumor emboli in the breast and breast skin lymphatics. IBC has been linked with obesity and duration of breastfeeding, but how these factors affect IBC tumor progression is not clear. We modeled the simultaneous effects of diet and weaning in mice on in vivo lymphatic function; on IBC tumor growth; and on aspects of the mammary gland microenvironment before and after IBC (SUM149) xenograft inoculation. We hypothesized that weaning status and diet would have synergistic effects on lymphatic function and the breast microenvironment to enhance IBC tumor growth. Changes in lymphatic structure and function were characterized with in vivo near-infrared fluorescence (NIRF) imaging. Mice were fed either a high-fat diet (HFD; 60 kcal%) or a normal/low-fat diet (LFD; 10 kcal%), bred twice, and subjected to either normal-duration nursing (NW) or forced weaning (FW). SUM149 IBC tumors were implanted at 14 months; images were obtained before and after implantation. Multiparous mice fed HFD showed increased pre-tumor lymphatic pulsing in both the FW and NW groups relative to mice fed LFD. HFD promoted tumor growth independent of weaning time (P = 0.04). Pre-tumor lymphatic pulsing was associated with tumor volume at 8 weeks (P = 0.02) and was significantly correlated with expression of the lymphatic tracking ligand CCL21 (P = 0.05, Table 1). HFD significantly increased the numbers of monocyte-derived IBA1+, CD163+, and CD11c+ cells (P < 0.0001, P < 0.0001, P = 0.0005) in the contralateral, non-tumor-bearing mammary gland. Numbers of lymphangiogenic podoplanin+/IBA1+ macrophages were increased in the ducts of HFD and FW mice (all P < 0.003). HFD in nulliparous mice had a similar increase in lymphatic pulsing at 14 weeks (P = 0.006), indicating that this functional change was independent of parity. We conclude that HFD induced increases in mammary gland lymphatic function, assessed as pulsing rate before tumor initiation, and correlated with inflammation in the mammary gland and increased SUM149 tumor growth. The relationship between diet, lymphatic pulsing, and tumor growth warrants further investigation.

The lymphatic system plays a fundamental role in cardiovascular physiology by maintaining whole-body fluid balance, facilitating immune trafficking, and enabling lipid transport. Through these functions, lymphatic performance is tightly coupled to cardiovascular health, and disturbances in lymphatic flow, pumping, or lympho-venous return can directly influence the development and progression of heart disease. This review examines the relationship between the lymphatic and cardiovascular systems with an emphasis on systemic lymphatic function and its relevance to cardiovascular pathology. We describe the structure and physiology of the human lymphatic vasculature, including mechanisms governing lymph formation, transport, and return to the venous circulation, and discuss how these processes are challenged in conditions such as heart failure, venous congestion, and altered hemodynamics. Clinical and experimental evidence linking lymphatic dysfunction to edema, inflammation, and impaired organ function across multiple cardiovascular disease states - including heart failure, atherosclerosis, congenital heart disease, and heart transplantation - is considered. In addition, comparative and translational perspectives are presented illustrating how diverse vertebrate lymphatic strategies inform fundamental principles of lymphatic regulation and translational cardiovascular research. Finally, emerging imaging modalities and therapeutic approaches targeting lymphatic structure and function are discussed as potential avenues for improving the diagnosis and treatment of cardiovascular disease. Together, this review positions the lymphatic system as an integral, system-level contributor to cardiovascular physiology and disease, underscoring the need to consider lymphatic function alongside the blood circulation in both research and clinical practice.

Over the past decade, we have begun to appreciate that the lymphatic vascular system does more than simply return plasma back into the circulatory system and, in fact, contributes to a wide variety of normal and disease states. For this reason, much research has been devoted to understanding how lymphatic vessels form and function, with a particular interest in which molecules contribute to lymphatic vessel growth and maintenance. In the following review, we focus on a potent lymphangiogenic factor, adrenomedullin, and its known roles in lymphangiogenesis, lymphatic function, and human lymphatic disease. As one of the first, pharmacologically tractable G protein-coupled receptor pathways characterized in lymphatic endothelial cells, the continued study of adrenomedullin effects on the lymphatic system may open new avenues for the modulation of lymphatic growth and function in a variety of lymphatic-related diseases that currently have few treatments.

In this study, we demonstrate that glycosylphosphatidylinositol (GPI) is a major toxin of Plasmodium falciparum origin responsible for nitric oxide (NO) production in host cells. Purified malarial GPI is sufficient to induce NO release in a time- and dose-dependent manner in macrophages and vascular endothelial cells, and regulates inducible NO synthase expression in macrophages. GPI-induced NO production was blocked by the NO synthase-specific inhibitor L-N-monomethylarginine. GPI also synergizes with IFN-gamma in regulating NO production. The structurally related molecules dipalmitoylphosphatidylinositol and iM4 glycoinositolphospholipid from Leishmania mexicana had no such activity, and the latter antagonized IFN-gamma-induced NO output. GPI activates macrophages by initiating an early onset tyrosine kinase-mediated signaling process, similar to that induced by total parasite extracts. The tyrosine kinase antagonists tyrphostin and genistein inhibited the release of NO by parasite extracts and by GPI, alone or in combination with IFN-gamma, demonstrating the involvement of one or more tyrosine kinases in the signaling cascade. GPI-induced NO release was also blocked by the protein kinase C inhibitor calphostin C, demonstrating a role for protein kinase C in GPI-mediated cell signaling, and by pyrrolidine dithiocarbamate, indicating the involvement of the NF-kappa B/c-rel family of transcription factors in cell activation. A neutralizing mAb to malarial GPI inhibited NO production induced by GPI and total malarial parasite extracts in human vascular endothelial cells and murine macrophages, indicating that GPI is a necessary agent of parasite origin in parasite-induced NO output. Thus, in contrast to dipalmitoylphosphatidylinositol and glycoinositolphospholipids of Leishmania, malarial GPI initiates a protein tyrosine kinase- and protein kinase C-mediated signal transduction pathway, regulating inducible NO synthase expression with the participation of NF-kappa B/c-rel, which leads to macrophage and vascular endothelial cell activation and downstream production of NO. These events may play a role in the etiology of severe malaria.