Elevated cutaneous leukocyte concentration in a rodent model of acute venous hypertension

Discovering Potential Compounds for Venous Disease Treatment through Virtual Screening and Network Pharmacology Approach

Peripheral venous hypertension has emerged as a prominent characteristic of venous disease (VD). This disease causes lower limb edema due to impaired blood transport in the veins. The phlebotonic drugs in use showed moderate evidence for reducing edema slightly in the lower legs and little or no difference in the quality of life. To enhance the probability of favorable experimental results, a virtual screening procedure was employed to identify molecules with potential therapeutic activity in VD. Compounds obtained from multiple databases, namely AC Discovery, NuBBE, BIOFACQUIM, and InflamNat, were compared with reference compounds. The examination of structural similarity, targets, and signaling pathways in venous diseases allows for the identification of compounds with potential usefulness in VD. The computational tools employed were rcdk and chemminer from R-Studio and Cytoscape. An extended fingerprint analysis allowed us to obtain 1846 from 41,655 compounds compiled. Only 229 compounds showed pharmacological targets in the PubChem server, of which 84 molecules interacted with the VD network. Because of their descriptors and multi-target capacity, only 18 molecules of 84 were identified as potential candidates for experimental evaluation. We opted to evaluate the berberine compound because of its affordability, and extensive literature support. The experiment showed the proposed activity in an acute venous hypertension model.

Time course of microvalve pathophysiology in high pressure low flow model of venous insufficiency and the role of micronized purified flavonoid fraction

BACKGROUND

The aim of this study was to characterize, in an experimental model, the mechanisms involved in the initiation of venous insufficiency at the level of microvenous valve and whether they can be influenced by early treatment with micronized purified flavonoid fraction (MPFF).

METHODS

The external right iliac vein of 78 male golden Syrian hamsters was ligated to induce chronic venous insufficiency. Internal venular diameter as well as leukocyteendothelium-interaction (leukocytes sticking after staining with rhodamine 6G), were assessed using an intravital microscope. In the second part of the study 30 animals were divided into three groups and underwent: ligation plus MPFF, ligation plus 10% lactose solution (vehicle), or sham operation. Treatment with MPFF 100 mg/kg/day or vehicle started 2 days before ligation and lasted for 7 days. Venular diameter and number of adherent leukocytes were assessed 5 days post-ligature.

RESULTS

Venule diameter increased immediately after ligature and reached a maximum at 4 hours (P<0.001 vs baseline), followed by a plateau before gradually returning to baseline dimensions. The increase in the number of adherent leukocytes was also immediate but attained maximal number at 3 days (p<0.0001), followed by a plateau and then gradual return to baseline numbers. In MPFF-treated animals, leukocyte adhesion to the microvalves was prevented compared with vehicle-treated animals (p<0.0001) and venule diameter was also significantly reduced (p<0.05).

CONCLUSIONS

Venous hypertension induced immediate venule dilatation followed by an increase in the number of adherent leukocytes at microvalve level. Treatment with MPFF prevented the initiation of microvalve inflammation and may play a protective role in the progression of chronic venous insufficiency.

Redox dysregulation in the pathogenesis of chronic venous ulceration

In chronic venous ulcers (CVUs), which account for up to 75% of leg ulcers, the inflammatory stage of wound healing fails to down-regulate, preventing progression to proliferation, remodeling and eventual epithelialisation. The roles of reactive oxygen species (ROS) in the oxidative burst and pathogen killing are well known, but ROS also have important functions in extra-cellular and intra-cellular signalling. Iron deposition, resulting from venous reflux, primes macrophages towards a persistent inflammatory response, with ongoing stimulation by bacteria potentially playing a role. Generation of excessive ROS by activated inflammatory cells causes tissue destruction and disintegration of the dermis, and then at later stages, a failure to heal. Here, we review the evidence for ROS in CVU formation and in normal and delayed healing. We also discuss how ROS modulation might be used to influence the healing of these complex wounds, which cause long-term morbidity and are associated with a significant financial burden to healthcare systems.

Protective Effects of Micronized Purified Flavonoid Fraction (MPFF) on a Novel Experimental Model of Chronic Venous Hypertension

OBJECTIVES

To assess protective effects of micronized purified flavonoid fraction (MPFF) on microcirculation in an original chronic model of hind limb venous hypertension with low blood flow in small animals.

METHODS

Vein ligatures were performed on male hamsters, as follows: A-right femoral vein; A + B-right femoral vein and its right branch; A + C-right femoral vein and its left branch; A + B + C-right femoral and its right and left branches; D-external right iliac vein. In sham operated groups, similar vascular dissections were performed without ligatures. Superficial (epigastric) and central (jugular) venous pressure evaluations were made during a 10 week period. Hamsters subjected to A + B + C and D ligatures were selected for leukocyte rolling and sticking, functional capillary density (FCD), and venular and arteriolar diameter observations. D ligature was selected to evaluate pharmacological treatment efficacy. MPFF (100 mg/kg), concomitant active flavonoids of MPFF (diosmetin, hesperidin, linarin, and isorhoifolin) (10 mg/kg), diosmin (100 mg/kg) or drug vehicle were administered orally during 2 weeks before vein ligature and 6 weeks thereafter.

RESULTS

A, A + B and A + C models maintained venous return through collaterals. From the 2^nd to the 10^th weeks after vein ligatures, A + B + C and D models elicited a progressive increase of superficial venous pressure (3.83 ± 0.65 vs. 8.56 ± 0.72 mmHg, p < .001 and 4.13 ± 0.65 vs. 9.35 ± 0.65 mmHg, p < .001, respectively) with significant changes to the microcirculation. As D model significantly increased superficial venous pressure without affecting central venous pressure, it was used to evaluate the long-term effects of treatment. Compared with vehicle, MPFF, concomitant active flavonoids of MPFF, and diosmin, significantly decreased leukocyte-endothelium interaction and prevented FCD reduction. Only MPFF significantly prevented venular enlargement as observed in the vehicle treated group.

CONCLUSION

MPFF was more effective than diosmin in improving all microvascular variables. The superiority of MPFF over diosmin alone can be explained by the synergistic beneficial effects of the association between diosmin and active flavonoids of MPFF.

Recommendations for the medical management of chronic venous disease: The role of Micronized Purified Flavanoid Fraction (MPFF)

Scope A systematic review of the clinical literature concerning medical management of chronic venous disease with the venoactive therapy Micronized Purified Flavonoid Fraction was conducted in addition to an investigation of the hemodynamics and mechanism of chronic venous disease. Methods The systematic review of the literature focused on the use of Micronized Purified Flavonoid Fraction (diosmin) which has recently become available in the US, in the management of chronic venous disease. The primary goal was to assess the level of evidence of the role of Micronized Purified Flavonoid Fraction in the healing of ulcers, and secondarily on the improvement of the symptoms of chronic venous disease such as edema. An initial search of Medline, Cochrane Database for Systematic Reviews and Google Scholar databases was conducted. The references of articles obtained in the primary search, including a Cochrane review of phlebotonics for venous insufficiency, were reviewed for additional studies. Studies were included if patients had a diagnosis of chronic venous disease documented with Doppler and Impedance Plethysmography. Studies excluded were those that had patients with arterial insufficiency (Ankle Brachial Index < .6), comorbidity of diabetes, obesity, rheumatological diseases, or if other causes of edema were present (congestive heart failure, renal, hepatic or lymphatic cause), or if the patient population had recent surgery or deep vein thrombosis, or had been using diuretics (in studies of edema). Other elements of the study design were to note specifically the type of compression therapy used in conjunction with Micronized Purified Flavonoid Fraction. Results The literature review yielded 250 abstracts, 65 of which met criteria for further review and 10 papers were selected for consideration in the systematic review. Conclusion In summary, the general level of evidence supports the recommendation that the use of medical therapy with Micronized Purified Flavonoid Fraction has beneficial outcomes without serious adverse events. In the United States, diosmiplex is the only available prescription formulation of Micronized Purified Flavonoid Fraction. It is derived from the rinds of oranges and is categorized as a medical food and not as a drug; and may be a particularly attractive therapy for many chronic venous disease patients because of its favorable safety profile. The Working Group for chronic venous disease concurs with previous guidance by the International European Society for Vascular Surgery in 2015 which recommended the use of Micronized Purified Flavonoid Fraction for the healing of venous ulcers, alone and adjunctive to compression therapy, and for the reduction in symptoms of chronic venous disease such as edema.

Effects of disturbed flow on vascular endothelium: pathophysiological basis and clinical perspectives

Vascular endothelial cells (ECs) are exposed to hemodynamic forces, which modulate EC functions and vascular biology/pathobiology in health and disease. The flow patterns and hemodynamic forces are not uniform in the vascular system. In straight parts of the arterial tree, blood flow is generally laminar and wall shear stress is high and directed; in branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress. Sustained laminar flow with high shear stress upregulates expressions of EC genes and proteins that are protective against atherosclerosis, whereas disturbed flow with associated reciprocating, low shear stress generally upregulates the EC genes and proteins that promote atherogenesis. These findings have led to the concept that the disturbed flow pattern in branch points and curvatures causes the preferential localization of atherosclerotic lesions. Disturbed flow also results in postsurgical neointimal hyperplasia and contributes to pathophysiology of clinical conditions such as in-stent restenosis, vein bypass graft failure, and transplant vasculopathy, as well as aortic valve calcification. In the venous system, disturbed flow resulting from reflux, outflow obstruction, and/or stasis leads to venous inflammation and thrombosis, and hence the development of chronic venous diseases. Understanding of the effects of disturbed flow on ECs can provide mechanistic insights into the role of complex flow patterns in pathogenesis of vascular diseases and can help to elucidate the phenotypic and functional differences between quiescent (nonatherogenic/nonthrombogenic) and activated (atherogenic/thrombogenic) ECs. This review summarizes the current knowledge on the role of disturbed flow in EC physiology and pathophysiology, as well as its clinical implications. Such information can contribute to our understanding of the etiology of lesion development in vascular niches with disturbed flow and help to generate new approaches for therapeutic interventions.

Effect of age on the biomechanical and microcirculatory properties of the skin in healthy individuals and during venous ulceration

BACKGROUND

With aging there is alteration of elastic properties of the skin and skin-blood flow.

AIM

The purpose of this study was to compare age-related changes in selected biomechanical parameters of the skin (skin hardness, skin extensibility, relaxation time constant, τ) and subcutaneous microcirculatory quality (SMQ) in individuals with and without venous diseases.

MATERIALS AND METHODS

TWO GROUPS WERE STUDIED: the first group was of asymptomatic healthy individuals and the second group included patients with chronic venous insufficiency (CVI) and venous ulceration, without edema. Both groups were subdivided to three age categories (21-40, 41-60 and 61-90 years old). Skin hardness was measured by durometer, extensibility and τ were measured using extensometer and SQM was assessed via postural vasoconstrictive response (LDF).

RESULTS

Results showed that skin hardness, extensibility, and τ-values were increased, whereas LDF was decreased in the older groups as compared with younger groups. These changes are attributed to alterations in the skin structure and reduced capillaries density networks. Similar behavior was found in the biomechanical and microcirculatory changes in patients with venous ulceration and CVI, but these changes were more increased further in older patients with venous ulceration as compared with older patients with CVI and that can be attribute to more intense response against tissue injury.

CONCLUSIONS

Since aging elevated skin hardness and extensibility, but lowered vasoconstrictive response in individuals, with and without, venous diseases, we conclude that aging process is likely to cause an accumulation of damaged skin tissues and that could induce an apparent antigen-driven response that altered skin structure and the subsequent biomechanical properties obtained in this study.

Molecular mechanisms in chronic venous insufficiency

Chronic venous disease (CVD) is common. Its manifestations include varicose veins; skin changes such as dermatitis, hyperpigmentation, and lipodermatosclerosis; and chronic leg ulcers. Recent advances in the understanding of its pathophysiology have shown how molecular mechanisms in the inflammatory cascade are involved in these diverse findings. Venous hypertension and associated fluid shear stress alterations on the endothelial surface may initiate this cascade and may lead to adverse changes in the venous wall, venous valves, and skin that can eventually result in varicose veins and in venous ulcers.

New advances in the understanding of the pathophysiology of chronic venous insufficiency

Chronic venous insufficiency (CVI) is inseparably linked to elevated venous pressure and is accompanied by vascular, dermal, and subcutaneous tissue damage and restructuring. Abundant evidence exists both in humans and in experimental models to suggest that the tissue damage may be initiated by generation of an inflammatory reaction. Inflammatory indicators include elevation of endothelial permeability; attachment of circulating leukocytes to the endothelium; infiltration of monocytes, lymphocytes, and mast cells into the connective tissue; and development of fibrotic tissue infiltrates and several molecular markers, such as growth factor or membrane adhesion molecule generation. Indicators of an inflammatory reaction are already detectable at early stages of CVI and may be involved in the development of primary venous valve dysfunction. One of the important questions is to identify trigger mechanisms for the inflammatory reaction in CVI. Current evidence suggests that, among several possible mechanisms (hypoxia, humoral stimulation), a shift in fluid shear stress from normal physiological levels and endothelial distension under the influence of elevated venous pressure may serve as trigger mechanisms for inflammation.

Evaluation of the role of intercellular adhesion molecule 1 in a rodent model of chronic venous hypertension

PURPOSE

To evaluate the role of intercellular adhesion molecule 1 (ICAM-1) in cutaneous leukocyte trapping in venous disease, we used our rodent model of venous hypertension (VH).

MATERIALS AND METHODS

VH was created in adult rats by ligation of the inferior vena cava, bilateral common iliac veins, and bilateral common femoral veins. In the Phase I experimental (exptl) group, anti-ICAM-1 monoclonal antibody (1A29) was given intravenously prior to venous ligations. Acute venous pressures were measured in the exptl and control (ctrl) (ligation only) groups. Bilateral forelimb and hindlimb skin specimens were harvested for myeloperoxidase (MPO) assay. In Phase II, VH was created in a chronic group; in a sham-operated group, ties were placed around the same vessels without ligations. Two weeks later, venous pressures were measured and radiolabeled ((125)I and (131)I) monoclonal antibody (mAb) to ICAM-1 was injected and allowed to circulate for 5 min before the level of radiolabeled antibody within forelimb and hindlimb specimens was measured.

RESULTS

In the acute study with 1A29, hindlimb pressures were significantly elevated in both the ctrl (n = 4) and exptl (n = 4) hindlimbs (15.4 +/- 0.239 and 13.8 +/- 1.89 mm Hg, respectively) compared with ctrl and exptl forelimbs (1.38 +/- 0.554 and 1.50 +/- 0.612 mm Hg, respectively). However, MPO activity was significantly elevated in the hindlimbs of the ctrl group compared with the hindlimbs of the exptl animals (19.8 +/- 1.54 U vs 6.71 +/- 2.46 U). In the chronic VH rats (n = 5) given radiolabeled anti-ICAM-1 mAb, the hindlimb pressures (10.1 +/- 4.52 mm Hg) were significantly elevated (P < 0.05) compared with forelimb pressures (1 +/- 0.447 mm Hg) and compared with the forelimb and hindlimb pressures in the sham-operated animals (n = 4) (1.63 +/- 0.813 and 4.25 +/- 2.13 mm Hg, respectively). However, there was not a significant difference in the quantity of ICAM-1-hindlimb versus forelimb or chronic VH versus sham.

CONCLUSIONS

Anti-ICAM-1 mAb decreased MPO activity in hypertensive hindlimb skin, supporting the instrumental role of ICAM-1 in cutaneous leukocyte trapping. However, the constituent endothelial ICAM-1 is not elevated by VH.

Increased hindlimb leukocyte concentration in a chronic rodent model of venous hypertension

BACKGROUND

The pathophysiologic mechanism for tissue damage in chronic venous insufficiency (CVI) is venous hypertension (VH), the primary mediator behind leukocyte trapping in tissues. We developed a new rodent model of chronic hindlimb VH to allow testing of the microvascular dysfunction that occurs in clinical CVI.

MATERIALS AND METHODS

Hindlimb VH was created in adult rats ( approximately 350 g, male, Wistar) by ligation of the inferior vena cava, bilateral common iliac veins, and bilateral common femoral veins. In a sham group, a loose tie was placed around the same vessels. One week later, pressure catheters were placed in the right common carotid artery, right internal jugular vein (forelimb), and right superficial epigastric vein (hindlimb). Measurements were taken 15 min later, to allow for stabilization. Bilateral forelimb and hindlimb skin specimens were harvested. The myeloperoxidase (MPO) assay, an indicator of tissue leukocyte trapping, was performed using a well-described, standard technique.

RESULTS

In the chronic rats (n = 8), the hindlimb pressures (12.6 +/- 3.2 mm Hg) were significantly elevated (P < 0.05) when compared to forelimb pressures (1.75 +/- 0.71) and to chronic sham rat (n = 6) hindlimb (3.3 +/- 1.2) pressures. There was a significant (P < 0.05) elevation of MPO activity in hindlimbs of the chronic group (32.9 +/- 13.9 units) when compared to forelimbs (17 +/- 11.3) and sham hindlimbs (18 +/- 10.2).

CONCLUSIONS

In our chronic model, as in clinical studies and previous acute investigations, we have demonstrated, using an MPO assay, an increase in the amount of cutaneous leukocytes in the hindlimbs with chronic VH but not in experimental forelimbs or sham hindlimbs or forelimbs.