Acute Metabolic Stress Induces Lymphatic Dysfunction Through KATP Channel Activation.

Lymphatic dysfunction is an underlying component of multiple metabolic diseases, including diabetes, obesity, and metabolic syndrome. We investigated the roles of KATP channels in lymphatic contractile dysfunction in response to acute metabolic stress induced by inhibition of the mitochondrial electron transport chain. Ex vivo popliteal lymphatic vessels from mice were exposed to the electron transport chain inhibitors antimycin A and rotenone, or the oxidative phosphorylation inhibitor/protonophore, CCCP.

Connexin-45 is expressed in mouse lymphatic endothelium and required for lymphatic valve function.

The expression and functional relevance of the gap junction molecule connexin-45 (Cx45; GJC1) in lymphatic endothelium were not previously known. We found that Cx45 was expressed widely in the endothelium of murine lymphatics, in both valve and nonvalve regions. Cell-specific deletion of Cx45, driven by a constitutive Cre line (Lyve1-Cre) or an inducible Cre line (Prox1-CreERT2), compromised the function of lymphatic valves, as assessed by physiological tests (back leak and closure) of isolated, single-valve vessel segments.

TRPV4-Expressing Tissue-Resident Macrophages Regulate the Function of Collecting Lymphatic Vessels via Thromboxane A2 Receptors in Lymphatic Muscle Cells.

Rationale: TRPV4 channels are critical regulators of blood vascular function and have been shown to be dysregulated in many disease conditions in association with inflammation and tissue fibrosis. These are key features in the pathophysiology of lymphatic system diseases, including lymphedema and lipedema; however, the role of TRPV4 channels in the lymphatic system remains largely unexplored. TRPV4 channels are calcium permeable, non-selective cation channels that are activated by diverse stimuli, including shear stress, stretch, temperature, and cell metabolites, which may regulate lymphatic contractile function.

Loss of anoctamin 1 reveals a subtle role for BK channels in lymphatic muscle action potentials.

Ca signalling plays a crucial role in determining lymphatic muscle cell excitability and contractility through its interaction with the Ca-activated Cl channel anoctamin 1 (ANO1). In contrast, the large-conductance (BK) Ca-activated K channel (KCa) and other KCa channels have prominent vasodilatory actions by hyperpolarizing vascular smooth muscle cells. Here, we assessed the expression and contribution of the KCa family to mouse and rat lymphatic collecting vessel contractile function.

Potentiating glymphatic drainage minimizes post-traumatic cerebral oedema.

Cerebral oedema is associated with morbidity and mortality after traumatic brain injury (TBI). Noradrenaline levels are increased after TBI, and the amplitude of the increase in noradrenaline predicts both the extent of injury and the likelihood of mortality. Glymphatic impairment is both a feature of and a contributor to brain injury, but its relationship with the injury-associated surge in noradrenaline is unclear.

Fibrinogen in mice cerebral microvessels induces blood-brain barrier dysregulation with aging via a dynamin-related protein 1-dependent pathway.

We previously reported evidence that oxidative stress during aging leads to adverse protein profile changes of brain cortical microvessels (MVs: end arterioles, capillaries, and venules) that affect mRNA/protein stability, basement membrane integrity, and ATP synthesis capacity in mice. As an extension of our previous study, we also found that proteins which comprise the blood-brain barrier (BBB) and regulate mitochondrial quality control were also significantly decreased in the mice's cortical MVs with aging. Interestingly, the neuroinflammatory protein fibrinogen (Fgn) was increased in mice brain MVs, which corresponds with clinical reports indicating that the plasma Fgn concentration increased progressively with aging.

IP3R1 underlies diastolic ANO1 activation and pressure-dependent chronotropy in lymphatic collecting vessels.

Pressure-dependent chronotropy of murine lymphatic collecting vessels relies on the activation of the Ca2+-activated chloride channel encoded by Anoctamin 1 (Ano1) in lymphatic muscle cells. Genetic ablation or pharmacological inhibition of ANO1 results in a significant reduction in basal contraction frequency and essentially complete loss of pressure-dependent frequency modulation by decreasing the rate of the diastolic depolarization phase of the ionic pacemaker in lymphatic muscle cells (LMCs). Oscillating Ca2+ release from sarcoendoplasmic reticulum Ca2+ channels has been hypothesized to drive ANO1 activity during diastole, but the source of Ca2+ for ANO1 activation in smooth muscle remains unclear.

Electric field stimulation unmasks a subtle role for T-type calcium channels in regulating lymphatic contraction.

We previously identified two isoforms of T-type, voltage-gated calcium (Ca3) channels (Ca3.1, Ca3.2) that are functionally expressed in murine lymphatic muscle cells; however, contractile tests of lymphatic vessels from single and double Ca3 knock-out (DKO) mice, exhibited nearly identical parameters of spontaneous twitch contractions as wild-type (WT) vessels, suggesting that Ca3 channels play no significant role.

Characterization of the cellular components of mouse collecting lymphatic vessels reveals that lymphatic muscle cells are the innate pacemaker cells regulating lymphatic contractions.

Collecting lymphatic vessels (cLVs) exhibit spontaneous contractions with a pressure-dependent frequency, but the identity of the lymphatic pacemaker cell is still debated. By analogy to pacemakers in the GI and lower urinary tracts, proposed cLV pacemaker cells include interstitial cells of Cajal like cells (ICLC) or the lymphatic muscle (LMCs) cells themselves. Here we combined immunofluorescence and scRNAseq analyses with electrophysiological methods to examine the cellular constituents of the mouse cLV wall and assess whether any cell type exhibited morphological and functional processes characteristic of pacemaker cells: a continuous if not contiguous network integrated into the electrical syncytium; spontaneous Ca transients; and depolarization-induced propagated contractions.

Postnatal development of extracellular matrix and vascular function in small arteries of the rat.

Vascular extracellular matrix (ECM) is dominated by elastic fibers (elastin with fibrillin-rich microfibrils) and collagens. Current understanding of ECM protein development largely comes from studies of conduit vessels (e.g.

Lymphatic contractile dysfunction in mouse models of Cantú Syndrome with K channel gain-of-function.

Cantú Syndrome (CS) is an autosomal dominant disorder caused by gain-of-function (GoF) mutations in the Kir6.1 and SUR2 subunits of K channels. K overactivity results in a chronic reduction in arterial tone and hypotension, leading to other systemic cardiovascular complications.

Circulating Plasma Exosomal Proteins of Either SHIV-Infected Rhesus Macaque or HIV-Infected Patient Indicates a Link to Neuropathogenesis.

Despite the suppression of human immunodeficiency virus (HIV) replication by combined antiretroviral therapy (cART), 50-60% of HIV-infected patients suffer from HIV-associated neurocognitive disorders (HAND). Studies are uncovering the role of extracellular vesicles (EVs), especially exosomes, in the central nervous system (CNS) due to HIV infection. We investigated links among circulating plasma exosomal (crExo) proteins and neuropathogenesis in simian/human immunodeficiency virus (SHIV)-infected rhesus macaques (RM) and HIV-infected and cART treated patients (Patient-Exo).

Multiple aspects of lymphatic dysfunction in an mouse model of hypercholesterolemia.

Rodent models of cardiovascular disease have uncovered various types of lymphatic vessel dysfunction that occur in association with atherosclerosis, type II diabetes and obesity. Previously, we presented evidence for impaired lymphatic drainage in apolipoprotein E null ( ) mice fed a high fat diet (HFD). Whether this impairment relates to the dysfunction of collecting lymphatics remains an open question.

ADAM17 cleaves the insulin receptor ectodomain on endothelial cells and causes vascular insulin resistance.

Inflammation and vascular insulin resistance are hallmarks of type 2 diabetes (T2D). However, several potential mechanisms causing abnormal endothelial insulin signaling in T2D need further investigation. Evidence indicates that the activity of ADAM17 (a disintegrin and metalloproteinase-17) and the presence of insulin receptor (IR) in plasma are increased in subjects with T2D.

Isolation and short-term culturing of primary lymphatic endothelial cells from collecting lymphatics: A techniques study.

Objective: To develop an experimental method for routine isolation and short-term culture of primary lymphatic endothelial cells from specific collecting vessels.

Methods: Lymphatic endothelial cell tubes (LECTs) were isolated from micro-dissected collecting vessels. LECTs were allowed to attach and grow for ~3 weeks before being passaged.

Lymphatic Valve Dysfunction in Western Diet-Fed Mice: New Insights Into Obesity-Induced Lymphedema.

A two-way connection between obesity and lymphatic dysfunction has now been established. Clinical studies have demonstrated that obesity significantly increases the risk for developing secondary lymphedema. Using animal-models, obesity and metabolic syndrome have been linked to different aspects of lymphatic structural abnormalities and lymphatic dysfunction, including impaired contractility, impaired flow-mediated responses, impaired fluid transport, as well as increased permeability, and abnormal dendritic cell migration among others.

Foxo1 deletion promotes the growth of new lymphatic valves.

Patients with congenital lymphedema suffer from tissue swelling in part due to mutations in genes regulating lymphatic valve development. Lymphatic valve leaflets grow and are maintained throughout life in response to oscillatory shear stress (OSS), which regulates gene transcription in lymphatic endothelial cells (LECs). Here, we identified the first transcription factor, Foxo1, that repressed lymphatic valve formation by inhibiting the expression of valve-forming genes.

Soil Lead (Pb) in New Orleans: A Spatiotemporal and Racial Analysis.

Spatialized racial injustices drive morbidity and mortality inequalities. While many factors contribute to environmental injustices, Pb is particularly insidious, and is associated with cardio-vascular, kidney, and immune dysfunctions and is a leading cause of premature death worldwide. Here, we present a revised analysis from the New Orleans dataset of soil lead (SPb) and children's blood Pb (BPb), which was systematically assembled for 2000-2005 and 2011-2016.

Effects of Elevated Downstream Pressure and the Role of Smooth Muscle Cell Coupling through Connexin45 on Lymphatic Pacemaking.

Lymphatic vessels rely on spontaneous lymphatic muscle cell (LMC) contractions and one-way intraluminal valves to efficiently pump lymph and return it into the bloodstream. Intraluminal pressure is known to regulate the contractile function of lymphatics, with pressure elevation leading to increased contraction frequency and decreased amplitude. Contractions are normally initiated by a dominant pacemaker and are highly entrained among strongly coupled LMCs.

Kir6.1-dependent K channels in lymphatic smooth muscle and vessel dysfunction in mice with Kir6.1 gain-of-function.

Key Points: Spontaneous contractions are essential for normal lymph transport and these contractions are exquisitely sensitive to the K channel activator pinacidil. K channel Kir6.1 and SUR2B subunits are expressed in mouse lymphatic smooth muscle (LSM) and form functional K channels as verified by electrophysiological techniques.

Simplified method to quantify valve back-leak uncovers severe mesenteric lymphatic valve dysfunction in mice deficient in connexins 43 and 37.

Key Points: Lymphatic valve defects are one of the major causes of lymph transport dysfunction; however, there are no accessible methods for quantitatively assessing valve function. This report describes a novel technique for quantifying lymphatic valve back-leak. Postnatal endothelial-specific deletion of connexin 43 (Cx43) in connexin 37 null (Cx37 ) mice results in rapid regression of valve leaflets and severe valve dysfunction.

T-type, but not L-type, voltage-gated calcium channels are dispensable for lymphatic pacemaking and spontaneous contractions.

The spontaneous contractions of collecting lymphatic vessels provide an essential propulsive force to return lymph centrally. These contractions are driven by an intrinsic electrical pacemaker, working through an unknown underlying ionic mechanism that becomes compromised in some forms of lymphedema. In previous studies, T-type voltage-gated Ca channels (VGCCs) were implicated in this pacemaking mechanism, based on the effects of the reputedly selective T-type VGCC inhibitors mibefradil and Ni.

Mechanisms of Connexin-Related Lymphedema.

Rationale: Mutations in GJC2 and GJA1, encoding Cxs (connexins) 47 and 43, respectively, are linked to lymphedema, but the underlying mechanisms are unknown. Because efficient lymph transport relies on the coordinated contractions of lymphatic muscle cells (LMCs) and their electrical coupling through Cxs, Cx-related lymphedema is proposed to result from dyssynchronous contractions of lymphatic vessels.

Objective: To determine which Cx isoforms in LMCs and lymphatic endothelial cells are required for the entrainment of lymphatic contraction waves and efficient lymph transport.