Histamine as an Endothelium-Derived Relaxing Factor in Aged Mesenteric Lymphatic Vessels

Edema and lymphatic clearance: molecular mechanisms and ongoing challenges

Resolution of edema remains a significant clinical challenge. Conditions such as traumatic shock, sepsis, or diabetes often involve microvascular hyperpermeability, which leads to tissue and organ dysfunction. Lymphatic insufficiency due to genetic causes, surgical removal of lymph nodes, or infections, leads to varying degrees of tissue swelling that impair mobility and immune defenses. Treatment options are limited to management of edema as there are no specific therapeutics that have demonstrated significant success for ameliorating microvascular leakage or impaired lymphatic function. This review examines current knowledge about the physiological, cellular, and molecular mechanisms that control microvascular permeability and lymphatic clearance, the respective processes for interstitial fluid formation and removal. Clinical conditions featuring edema, along with potential future directions are discussed.

In Vitro and In Vivo Characterization of the Transdermal Gel Formulation of Desloratadine for Prevention of Obesity and Metabolic Syndrome

Chronic use of antihistamines can induce abnormalities in lipid absorption with potential excessive accumulation of lipids in the mesentery that can lead to the development of obesity and a metabolic syndrome. The focus of the present work was to develop a transdermal gel formulation of desloratadine (DES) to prevent/reduce obesity and metabolic syndromes. Nine formulations were prepared to contain hydroxypropyl methylcellulose (2-3%), DES (2.5-5.0%), and Transcutol^® (15-20%). The formulations were evaluated for cohesive and adhesive properties, viscosity, drug diffusion through synthetic and pig ear skin, and pharmacokinetics in New Zealand white rabbits. Drug permeation was faster through the skin compared to synthetic membranes. The drug had good permeation, as indicated by very short lag time (0.08-0.47 h) and high flux (59.3-230.7 μg/cm².h). The maximum plasma concentration (C_max) and area under the curve (AUC) of transdermal gel formulations were 2.4 and 3.2 fold that of the Clarinex tablet formulation. In conclusion, as indicated by the higher bioavailability, transdermal gel formulation of DES may decrease the dose of the drug, compared to commercial formulation. It has the potential to reduce or eliminate metabolic syndromes associated with oral antihistamine therapy.

Lymphatic Clearance and Pump Function

Lymphatic vessels have an active role in draining excess interstitial fluid from organs and serving as conduits for immune cell trafficking to lymph nodes. In the central circulation, the force needed to propel blood forward is generated by the heart. In contrast, lymphatic vessels rely on intrinsic vessel contractions in combination with extrinsic forces for lymph propulsion. The intrinsic pumping features phasic contractions generated by lymphatic smooth muscle. Periodic, bicuspid valves composed of endothelial cells prevent backflow of lymph. This work provides a brief overview of lymph transport, including initial lymph formation along with cellular and molecular mechanisms controlling lymphatic vessel pumping.

Effect of the snake venom component crotamine on lymphatic endothelial cell responses and lymph transport

OBJECTIVE

The pathology of snake envenomation is closely tied to the severity of edema in the tissue surrounding the area of the bite. Elucidating the mechanisms that promote the development of such severe edema is critical to a better understanding of how to treat this life-threatening injury. We focused on one of the most abundant venom components in North American viper venom, crotamine, and the effects it has on the cells and function of the lymphatic system.

METHODS

We used RT-PCR to identify the location and relative abundance of crotamine's cellular targets (Kvα channels) within the tissues and cells of the lymphatic system. We used calcium flux, nitrate production, and cell morphometry to determine the effects of crotamine on lymphatic endothelial cells. We used tracer transport, node morphometry, and node deposition to determine the effects of crotamine on lymph transport in vivo.

RESULTS

We found that genes that encode targets of crotamine are highly present in lymphatic tissues and cells and that there is a differential distribution of those genes that correlates with phasic contractile activity. We found that crotamine potentiates calcium flux in human dermal lymphatic endothelial cells in response to stimulation with histamine and sheer stress (but not alone) and that it alters the production of nitric oxide in response to shear as well as changes the level of F-actin polymerization of those same cells. Crotamine alters lymphatic transport of large molecular weight tracers to local lymph nodes and is deposited within the node mostly in the immediate subcapsular region.

CONCLUSION

This evidence suggests that snake venom components may have an impact on the function of the lymphatic system. This needs to be studied in greater detail as there are numerous venom components that may have effects on aspects of the lymphatic system. This would not only provide basic information on the pathobiology of snakebite but also provide targets for improved therapeutics to treat snakebite.

Lymphatic Contractile Function: A Comprehensive Review of Drug Effects and Potential Clinical Application

BACKGROUND

The lymphatic system and the cardiovascular 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 cardiovascular 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 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.

AIM

To identify (1) drugs with direct effects on lymphatic tonic and phasic contractions with potential for clinical application, and (2) drugs in current clinical use that have a positive or negative side effect on lymphatic function.

METHODS

We comprehensively reviewed all studies that tested the direct effect of a drug on the contractile function of lymphatic vessels.

RESULTS

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 FDA-approved drugs, there were 14 that increased lymphatic phasic contractile function. The most frequently used class of drug with inhibitory effects on lymphatic pump function were the calcium channels blockers.

CONCLUSION

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.

Lymphatic Senescence: Current Updates and Perspectives

Simple Summary

The lymphatic system is involved in tissue homeostasis, immune processes as well as transport of lipids, proteins and pathogens. Aging affects all physiological systems. However, it is not well studied how aging affects the lymphatic vasculature. Therefore, this review aims at investigating how senescence could lead to changes in the structure and function of the lymphatic vessels. We report that lymphatic senescence is associated with alterations in lymphatic muscles and nerve fibers, lymphatic endothelial cells membrane dysfunction, as well as changes in lymphatic pump, acute inflammation responses and immune function.

Abstract

Lymphatic flow is necessary for maintenance of vital physiological functions in humans and animals. To carry out optimal lymphatic flow, adequate contractile activity of the lymphatic collectors is necessary. Like in all body systems, aging has also an effect on the lymphatic system. However, limited knowledge is available on how aging directly affects the lymphatic system anatomy, physiology and function. We investigated how senescence leads to alterations in morphology and function of the lymphatic vessels. We used the strategy of a review to summarize the scientific literature of studies that have been published in the area of lymphatic senescence. Searches were carried out on PubMed and Web of Science using predefined search queries. We obtained an initial set of 1060 publications. They were filtered to 114 publications based on strict inclusion and exclusion criteria. Finally, the most appropriate 57 studies that specifically addressed lymphatic senescence have been selected for the preparation of this review. Analysis of the literature showed that lymphatic senescence is associated with alterations in lymphatic muscles and nerve fibers, lymphatic glycocalyx function of lymphatic endothelial cells, effects of chronic ultraviolet light exposure and oxidative stress as well as changes in lymphatic pump, acute inflammation responses and immune function. The current review underscores the relevance of the understudied area of lymphatic senescence. Continued research on the impact of aging on the structure and function of the lymphatic vasculature is needed to provide further insights to develop innovative clinical diagnostic—and treatment—modalities as well as to reduce the morbidity associated with diseases related to the lymphatic system.

Antihistamines Increase Body Mass Index Percentiles and Z-Scores in Hispanic Children

The prevalence of childhood obesity has increased over the years in the United States and contributed to a rise in metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). Animal studies suggested the role of histamine blockade on mesenteric lymphatics tone, contributing to weight gain and hepatic steatosis. This study aimed to investigate an association between antihistamines (AH) use in children and obesity. A single-center retrospective cohort study on children with a diagnosis of NAFLD, followed in the gastroenterology clinic, was performed between January 2018 and April 2019. The demographics, medications, and body mass index (BMI) were assessed. Participants were divided into an AH group with documented use and comparison group, antihistamine naïve. Of the 32 participants in the study, 13 used AH, and 19 did not. Antihistamine users had a mean increase in BMI percentile per year of 1.17 compared to a decrease of 0.06 in comparison group (p = 0.0008). AH usage correlated with a mean increase in BMI z-score of 0.23 per year, as opposed to a decrease by 0.012 in comparison group (p = 0.0016). No difference was found in triglycerides (TG), glucose, and liver enzymes. AH use increases BMI percentiles and z-scores over time and is associated with obesity in children.

The Role of Lymphatics in Cholestasis: A Comprehensive Review

Cholestatic liver disease affects millions of people worldwide and stems from a plethora of causes such as immune dysfunction, genetics, cancerous growths, and lifestyle choices. While not considered a classical lymphatic organ, the liver plays a vital role in the lymph system producing up to half of the body's lymph per day. The lymphatic system is critical to the health of an organism with its networks of vessels that provide drainage for lymphatic fluid and routes for surveilling immune cells. Cholestasis results in an increase of inflammatory cytokines, growth factors, and inflammatory infiltrate. Left unchecked, further disease progression will include collagen deposition which impedes both the hepatic and lymphatic ducts, eventually resulting in an increase in hepatic decompensation, increasing portal pressures, and accumulation of fluid within the abdominal cavity (ascites). Despite the documented interplay between these vital systems, little is known about the effect of liver disease on the lymph system and its biological response. This review looks at the current cholestatic literature from the perspective of the lymphatic system and summarizes what is known about the role of the lymph system in liver pathogenesis during hepatic injury and remodeling, immune-modulating events, or variations in interstitial pressures.

Characterization of rat tail lymphatic contractility and biomechanics: incorporating nitric oxide-mediated vasoregulation

The lymphatic system transports lymph from the interstitial space back to the great veins via a series of orchestrated contractions of chains of lymphangions. Biomechanical models of lymph transport, validated with ex vivo or in vivo experimental results, have proved useful in revealing novel insight into lymphatic pumping; however, a need remains to characterize the contributions of vasoregulatory compounds in these modelling tools. Nitric oxide (NO) is a key mediator of lymphatic pumping. We quantified the active contractile and passive biaxial biomechanical response of rat tail collecting lymphatics and changes in the contractile response to the exogenous NO administration and integrated these findings into a biomechanical model. The passive mechanical response was characterized with a three-fibre family model. Nonlinear regression and non-parametric bootstrapping were used to identify best-fit material parameters to passive cylindrical biaxial mechanical data, assessing uniqueness and parameter confidence intervals; this model yielded a good fit (R² = 0.90). Exogenous delivery of NO via sodium nitroprusside (SNP) elicited a dose-dependent suppression of contractions; the amplitude of contractions decreased by 30% and the contraction frequency decreased by 70%. Contractile function was characterized with a modified Rachev-Hayashi model, introducing a parameter that is related to SNP concentration; the model provided a good fit (R² = 0.89) to changes in contractile responses to varying concentrations of SNP. These results demonstrated the significant role of NO in lymphatic pumping and provide a predictive biomechanical model to integrate the combined effect of mechanical loading and NO on lymphatic contractility and mechanical response.

Emerging Roles of Mast Cells in the Regulation of Lymphatic Immuno-Physiology

Mast cells (MCs) are abundant in almost all vascularized tissues. Furthermore, their anatomical proximity to lymphatic vessels and their ability to synthesize, store and release a large array of inflammatory and vasoactive mediators emphasize their significance in the regulation of the lymphatic vascular functions. As a major secretory cell of the innate immune system, MCs maintain their steady-state granule release under normal physiological conditions; however, the inflammatory response potentiates their ability to synthesize and secrete these mediators. Activation of MCs in response to inflammatory signals can trigger adaptive immune responses by dendritic cell-directed T cell activation. In addition, through the secretion of various mediators, cytokines and growth factors, MCs not only facilitate interaction and migration of immune cells, but also influence lymphatic permeability, contractility, and vascular remodeling as well as immune cell trafficking through the lymphatic vessels. In summary, the consequences of these events directly affect the lymphatic niche, influencing inflammation at multiple levels. In this review, we have summarized the recent advancements in our understanding of the MC biology in the context of the lymphatic vascular system. We have further highlighted the MC-lymphatic interaction axis from the standpoint of the tumor microenvironment.

Histidine in Health and Disease: Metabolism, Physiological Importance, and Use as a Supplement

L-histidine (HIS) is an essential amino acid with unique roles in proton buffering, metal ion chelation, scavenging of reactive oxygen and nitrogen species, erythropoiesis, and the histaminergic system. Several HIS-rich proteins (e.g., haemoproteins, HIS-rich glycoproteins, histatins, HIS-rich calcium-binding protein, and filaggrin), HIS-containing dipeptides (particularly carnosine), and methyl- and sulphur-containing derivatives of HIS (3-methylhistidine, 1-methylhistidine, and ergothioneine) have specific functions. The unique chemical properties and physiological functions are the basis of the theoretical rationale to suggest HIS supplementation in a wide range of conditions. Several decades of experience have confirmed the effectiveness of HIS as a component of solutions used for organ preservation and myocardial protection in cardiac surgery. Further studies are needed to elucidate the effects of HIS supplementation on neurological disorders, atopic dermatitis, metabolic syndrome, diabetes, uraemic anaemia, ulcers, inflammatory bowel diseases, malignancies, and muscle performance during strenuous exercise. Signs of toxicity, mutagenic activity, and allergic reactions or peptic ulcers have not been reported, although HIS is a histamine precursor. Of concern should be findings of hepatic enlargement and increases in ammonia and glutamine and of decrease in branched-chain amino acids (valine, leucine, and isoleucine) in blood plasma indicating that HIS supplementation is inappropriate in patients with liver disease.

Pathophysiology of aged lymphatic vessels

Lymphatic vessels maintain body homeostasis by recirculation of fluid and cells. Cell senescence induces lymphatic dysfunction. Impaired contractile function is caused by low muscle cell investiture and decrease of nitric oxide in aged lymphatic collectors, leading to poor drainage of lymph. Aging-induced loss of endothelial glycocalyx and production of inflammatory cytokines increases permeability of lymphatic vessels. In addition, aging-associated basal activation of mast cells delays immune response. In this review, we summarize the structural and pathological changes of aged lymphatic vessels, and discuss the underlying molecular mechanisms.

Histamine-Receptor Antagonists Slow 10-km Cycling Performance in Competitive Cyclists

Histamine is released within skeletal muscle during exercise. In humans, antihistamines have no effect on speed, power output, or time-to-completion of short-duration high-intensity exercise. In mice, blocking histamine's actions decreases speed and duration of endurance tasks. It is unknown if these opposing outcomes are the result of differences in histamine's actions between species or are related to duration and/or intensity of exercise, as blocking histamine during endurance exercise has not been examined in humans.

PURPOSE

Determine the effects of histamine-receptor antagonism on cycling time trial performance in humans, with and without a preceding bout of sustained steady-state exercise.

METHODS

Eleven (3F) competitive cyclists performed six 10-km time trials on separate days. The first two time trials served as familiarization. The next four time trials were performed in randomized-block order, where two were preceded by 120 min of seated rest (rest) and two by 120 min of cycling exercise (Exercise) at 50% V˙O2peak. Within each block, subjects consumed either combined histamine H1 and H2 receptor antagonists (Blockade) or Placebo, before the start of the 120-min Rest/Exercise.

RESULTS

Blockade had no discernible effects on hemodynamic or metabolic variables during Rest or Exercise. However, Blockade increased time-to-completion of the 10-km time trial compared with Placebo (+10.5 ± 3.7 s, P < 0.05). Slowing from placebo to blockade was not different between rest (+8.7 ± 5.2 s) and Exercise (+12.3 ± 5.8 s, P = 0.716).

CONCLUSIONS

Exercise-related histaminergic signaling appears inherent to endurance exercise and may play a role in facilitating optimal function during high-intensity endurance exercise.

Prolonged intake of desloratadine: mesenteric lymphatic vessel dysfunction and development of obesity/metabolic syndrome

This study aimed to establish mechanistic links between the prolonged intake of desloratadine, a common H1 receptor blocker (i.e., antihistamine), and development of obesity and metabolic syndrome. Male Sprague-Dawley rats were treated for 16 wk with desloratadine. We analyzed the dynamics of body weight gain, tissue fat accumulation/density, contractility of isolated mesenteric lymphatic vessels, and levels of blood lipids, glucose, and insulin, together with parameters of liver function. Prolonged intake of desloratadine induced development of an obesity-like phenotype and signs of metabolic syndrome. These alterations in the body included excessive weight gain, increased density of abdominal subcutaneous fat and intracapsular brown fat, high blood triglycerides with an indication of their rerouting toward portal blood, high HDL, high fasting blood glucose with normal fasting and nonfasting insulin levels (insulin resistance), high liver/body weight ratio, and liver steatosis (fatty liver). These changes were associated with dysfunction of mesenteric lymphatic vessels, specifically high lymphatic tone and resistance to flow together with diminished tonic and abolished phasic responses to increases in flow, (i.e., greatly diminished adaptive reserves to respond to postprandial increases in lymph flow). The role of nitric oxide in this flow-dependent adaptation was abolished, with remnants of these responses controlled by lymphatic vessel-derived histamine. Our current data, considered together with reports in the literature, support the notion that millions of the United States population are highly likely affected by underevaluated, lymphatic-related side effects of antihistamines and may develop obesity and metabolic syndrome due to the prolonged intake of this medication. NEW & NOTEWORTHY Prolonged intake of desloratadine induced development of obesity and metabolic syndrome associated with dysfunction of mesenteric lymphatic vessels, high lymphatic tone, and resistance to flow together with greatly diminished adaptive reserves to respond to postprandial increases in lymph flow. Data support the notion that millions of the USA population are highly likely affected by underevaluated, lymphatic-related side effects of antihistamines and may develop obesity and metabolic syndrome due to the prolonged intake of this medication.

Lymphatic Vessel Network Structure and Physiology

The lymphatic system is comprised of a network of vessels interrelated with lymphoid tissue, which has the holistic function to maintain the local physiologic environment for every cell in all tissues of the body. The lymphatic system maintains extracellular fluid homeostasis favorable for optimal tissue function, removing substances that arise due to metabolism or cell death, and optimizing immunity against bacteria, viruses, parasites, and other antigens. This article provides a comprehensive review of important findings over the past century along with recent advances in the understanding of the anatomy and physiology of lymphatic vessels, including tissue/organ specificity, development, mechanisms of lymph formation and transport, lymphangiogenesis, and the roles of lymphatics in disease. © 2019 American Physiological Society. Compr Physiol 9:207-299, 2019.

Temporal Dynamics of the Rat Thoracic Duct Contractility in the Presence of Imposed Flow

BACKGROUND

The initial periods of increased flow inside lymphatic vessels demonstrate specific temporary patterns of self-tuning of lymphatic vessel contractility that are heterogeneous across regional lymphatic networks. The current literature primarily refers to the immediate and fast reactions of the lymphangions to increases in basal flow. Until now, there were no available data on how the lymphatic vessels react to comparatively longer periods of imposed flow.

METHODS AND RESULTS

In this study, we measured and analyzed the contractility of the rat thoracic duct segments, isolated, cannulated, and pressurized at 3 cm H₂O at no imposed flow conditions and during 4 hours of imposed flow (constant transaxial pressure gradient of 2 cm H₂O). We found the development of a progressing lymphatic tonic relaxation and inhibition of the lymphatic contraction frequency over 4 hours of imposed flow. After a short initial decrease, lymphatic phasic contraction amplitude rose significantly during the first hour of imposed flow, and it demonstrated a trend to return toward control levels after 3 hours of imposed flow. As a result, the fractional pump flow (active lymph pumping per minute) of isolated thoracic duct segments reached and maintained a statistically significant decrease (from control no-flow conditions) at the end of the third hour of imposed flow.

CONCLUSIONS

Our new findings provide a better understanding of how lymphatic contractility changes during the development of prolonged periods of steady lymph flow. The latter may occur during the initial phases of development of an inflammatory-related tissue edema.

Aged Lymphatic Vessels and Mast Cells in Perilymphatic Tissues

This review provides a comprehensive summary of research on aging-associated alterations in lymphatic vessels and mast cells in perilymphatic tissues. Aging alters structure (by increasing the size of zones with low muscle cell investiture), ultrastructure (through loss of the glycocalyx), and proteome composition with a concomitant increase in permeability of aged lymphatic vessels. The contractile function of aged lymphatic vessels is depleted with the abolished role of nitric oxide and an increased role of lymphatic-born histamine in flow-dependent regulation of lymphatic phasic contractions and tone. In addition, aging induces oxidative stress in lymphatic vessels and facilitates the spread of pathogens from these vessels into perilymphatic tissues. Aging causes the basal activation of perilymphatic mast cells, which, in turn, restricts recruitment/activation of immune cells in perilymphatic tissues. This aging-associated basal activation of mast cells limits proper functioning of the mast cell/histamine/NF-κB axis that is essential for the regulation of lymphatic vessel transport and barrier functions as well as for both the interaction and trafficking of immune cells near and within lymphatic collecting vessels. Cumulatively, these changes play important roles in the pathogenesis of alterations in inflammation and immunity associated with aging.