Vasculotide, an Angiopoietin-1 mimetic, reduces acute skin ionizing radiation damage in a preclinical mouse model

Jia-Wei-Si-Miao-Yong-An Fang stimulates the healing of acute radiation-induced cutaneous wounds through MAPK/ERK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

A famous traditional oral Chinese medicine formula, Si-Miao-Yong-An decoction, has been used to treat thromboangiitis obliterans from the Qing Dynasty. Because its therapeutic principles including clearing away heat, detoxification, accelerating blood circulation and relieving pains are consistent with acute radiation-induced cutaneous wounds in traditional Chinese medicine, we tried to add herbs and improve them into an external dosage form, called Jia-Wei-Si-Miao-Yong-An Fang (JWSMYA). However, its mechanism on radiation-induced cutaneous wounds is still unknown.

AIM OF THE STUDY

This study evaluated the therapeutic effect of JWSMYA and investigated the mechanism of repair and anti-fibrosis on acute radiation-induced cutaneous wounds with JWSMYA.

MATERIALS AND METHODS

Firstly, we prepared JWSMYA, and determined the composition through UHPLC LC-MS/MS. Then we used ionizing radiation to make a cutaneous wound model of rats, and observed wound healing through their skin injury score, wound contraction percentage and histological staining. In addition, immunohistochemical staining, Western blot analysis, qRT-PCR and Elisa were used to explore wound rehabilitation and anti-fibrosis mechanisms.

RESULTS

An in vivo assay revealed that JWSMYA promoted the repairment of acute radiation-induced cutaneous wounds, facilitated MAPK/ERK phosphorylation, inhibited PI3K/AKT activation, reduced the level of alpha-smooth muscle actin (a-sma), collagen type-I alpha 2 (Col1a2) and transforming growth factor-beta 1 (TGF-β1) in cutaneous tissues. However, no statistical difference was found in vascular endothelial growth factor (VEGF).

CONCLUSION

JWSMYA accelerated the repair of acute radiation-induced cutaneous wounds, which might be associated with the MAPK/ERK pathway. In addition, PI3K/AKT might be associated with the inhibition of fibrosis and the promotion of high-quality wound healing.

Treatment With an Angiopoietin-1 Mimetic Peptide Improves Cognitive Outcome in Rats With Vascular Dementia

Background and Purpose

Vascular dementia (VaD) is a complex neurodegenerative disease affecting cognition and memory. There is a lack of approved pharmacological treatments specifically for VaD. In this study, we investigate the therapeutic effects of AV-001, a Tie2 receptor agonist, in middle-aged rats subjected to a multiple microinfarct (MMI) model of VaD.

Methods

Male, 10-12 month-old, Wistar rats were employed. The following experimental groups were used: Sham, MMI, MMI+1 μg/Kg AV-001, MMI+3 μg/Kg AV-001, MMI+6 μg/Kg AV-001. AV-001 treatment was initiated at 1 day after MMI and administered once daily via intraperitoneal injection. An investigator blinded to the experimental groups conducted a battery of neuro-cognitive tests including modified neurological severity score (mNSS) test, novel object recognition test, novel odor recognition test, three chamber social interaction test, and Morris water maze test. Rats were sacrificed at 6 weeks after MMI.

Results

There was no mortality observed after 1, 3, or 6 μg/Kg AV-001 treatment in middle-aged rats subjected to MMI. AV-001 treatment (1, 3, or 6 μg/Kg) does not significantly alter blood pressure or heart rate at 6 weeks after MMI compared to baseline values or the MMI control group. Treatment of MMI with 1 or 3 μg/Kg AV-001 treatment does not significantly alter body weight compared to Sham or MMI control group. While 6 μg/Kg AV-001 treated group exhibit significantly lower body weight compared to Sham and MMI control group, the weight loss is evident starting at 1 day after MMI when treatment was initiated and is not significantly different compared to its baseline values at day 0 or day 1 after MMI. AV-001 treatment significantly decreases serum alanine aminotransferase, serum creatinine, and serum troponin I levels compared to the MMI control group; however, all values are within normal range. MMI induces mild neurological deficits in middle-aged rats indicated by low mNSS scores (<6 on a scale of 0-18). Compared to control MMI group, 1 μg/Kg AV-001 treatment group did not exhibit significantly different mNSS scores, while 3 and 6 μg/Kg AV-001 treatment induced significantly worse mNSS scores on days 21-42 and 14-42 after MMI, respectively. MMI in middle-aged rats induces significant cognitive impairment including short-term memory loss, long-term memory loss, reduced preference for social novelty and impaired spatial learning and memory compared to sham control rats. Rats treated with 1 μg/Kg AV-001 exhibit significantly improved short-term and long-term memory, increased preference for social novelty, and improved spatial learning and memory compared to MMI rats. Treatment with 3 μg/Kg AV-001 improves short-term memory and preference for social novelty but does not improve long-term memory or spatial learning and memory compared to MMI rats. Treatment with 6 μg/Kg AV-001 improves only long-term memory compared to MMI rats. Thus, 1 μg/Kg AV-001 treatment was selected as an optimal dose. Treatment of middle-aged rats subjected to MMI with 1 μg/Kg AV-001 significantly increases axon density, myelin density and myelin thickness in the corpus callosum, as well as increases synaptic protein expression, neuronal branching and dendritic spine density in the cortex, oligodendrocytes and oligodendrocyte progenitor cell number in the cortex and striatum and promotes neurogenesis in the subventricular zone compared to control MMI rats.

Conclusions

In this study, we present AV-001 as a novel therapeutic agent to improve cognitive function and reduce white matter injury in middle aged-rats subjected to a MMI model of VaD. Treatment of MMI with 1 μg/Kg AV-001 significantly improves cognitive function, and increases axon density, remyelination and neuroplasticity in the brain of middle-aged rats.

Hypoxanthine Reduces Radiation Damage in Vascular Endothelial Cells and Mouse Skin by Enhancing ATP Production via the Salvage Pathway

An effective method that can protect radiation-damaged tissues from apoptosis and promote tissue repair has not been reported to date. Hypoxanthine (Hx) is an intermediate metabolite in the purine degradation system that serves as a substrate for ATP synthesis via the salvage pathway. In this study, we focused on the transient decrease in intracellular ATP concentration after radiation exposure and examined the protective effect of Hx against radiation-induced tissue damage. Human umbilical vein endothelial cells were X irradiated, and the cell viability and incidence of apoptosis and DNA double-strand breaks (DSBs) were evaluated at different Hx concentrations. We found that in the presence of 2-100 μM Hx, the percentages of DSBs and apoptotic cells after 2, 6 and 10 Gy dose of radiation significantly decreased, whereas cell viability increased in a concentration-dependent manner. Moreover, the addition of Hx increased the levels of AMP, ADP, and ATP in the cells at 2 h postirradiation, suggesting that Hx was used for adenine nucleotide synthesis through the salvage pathway. Administration of a xanthine oxidoreductase inhibitor to a mouse model of radiation dermatitis resulted in increased blood Hx levels that inhibited severe dermatitis and accelerated recovery. In conclusion, the findings provide evidence that increasing the levels of Hx to replenish ATP could be an effective strategy to reduce radiation-induced tissue damage and elucidating the detailed mechanisms underlying the protective effects of Hx could help develop new protective strategies against radiation.

A balanced charged hydrogel with anti-biofouling and antioxidant properties for treatment of irradiation-induced skin injury

Skin injury caused by large doses of ionizing radiation is the common and severe side effect of radiotherapy. However, its therapeutic efficacy is always hindered by early reactive oxygen species generation, repetitive inflammatory microenvironment and bacterial infection risk. Herein, we report an anti-biofouling hydrogel with anti-inflammation and anti-oxidative properties for the treatment of irradiation-induced skin injury. The anti-biofouling hydrogel can be achieved by balancing oppositely charged alginate, hyaluronic acid (HA) and polylysine (PLL) at the optimal ratio, which effectively resist protein and bacterial adhesion, and evades immune response. Moreover, curcumin and epigallocatechin gallate (EGCG) can be facially encapsulated and substantially released from the hydrogel. Results showed that the resulting AHP-Cur/EGCG hydrogel can significantly weaken the development of skin injury and accelerate its healing process by alleviating inflammation, scavenging ROS and promoting angiogenesis. Therefore, the findings presented in this work provide an effective strategy for clinical management and treatment of ionizing radiation-induced skin injury.

Topical application of Jatyadi Ghrita and Jatyadi Taila accelerates wound healing in Sprague-Dawley rats: a study in gamma-radiation-induced skin wound model

PURPOSE

Radiation-induced skin wounds/dermatitis can occur due to therapeutic, occupational, or accidental exposure to ionizing radiation. This study investigated the therapeutic efficacy of standardized Ayurvedic formulations [Jatyadi ghrita (JG) and Jatyadi taila (JT)] against 60Co-γ-radiation-induced acute skin wounds in rats.

MATERIAL AND METHODS

Animal's [Sprague-Dawley rats (200 ± 20 g)] flanked skin was locally exposed to 45 Gy radiation (R45Gy) in Cobalt-60-teletherapy unit (Bhabhatron) to generate radiation wounds. JG and JT were applied topically twice daily on wounds from day 14 onwards after appearance of moist desquamation and wound healing efficacy was observed for a period of 42 days.

RESULTS

R45Gy induced significant time dependent changes in rat's skin with erythema on day 7 followed by dry and moist desquamation. JG and JT application significantly (p < .001) reduced skin damage score, wound area (92% and 97% respectively on day 42), and bacterial load, when compared with R45Gy and showed better efficacy than sucralfate and betamethasone (positive controls). Formulations significantly reduced lipid peroxidation and enhanced antioxidant defenses, reduced inflammatory infiltrates and collagen fibers deposition as evident by decreased myeloperoxidase and hydroxyproline levels, and also reduced transforming growth factor-beta 1 (TGF-β1) expression. Further, histology revealed reduced epidermal hyperplasia and dermal thinning with improved densities of hair follicles. Formulations were found to be nontoxic on 28 days application.

CONCLUSIONS

The results demonstrated that JG and JT accelerated wound healing in irradiated skin tissue by faster re-epithelialization; reducing inflammation, collagen fibers deposition, and TGF-β1 expression, indicated their potential human application in countering radiation wounds.

The Effects of Human Bone Marrow-Derived Mesenchymal Stem Cell Conditioned Media Produced with Fetal Bovine Serum or Human Platelet Lysate on Skin Rejuvenation Characteristics

Background and Objectives

Human mesenchymal stem cell-conditioned medium (MSC-CM) is produced using mesenchymal stem cell culture technology and has various benefits for the skin, including wrinkle removal, skin regeneration, and increased antioxidant activity. Its popularity is thus increasing in the field of functional cosmetics.

Methods and Results

In this study, we analyzed the effects of fetal bovine serum-supplemented MSC-CM (FBS- MSC-CM) and human platelet lysate-supplemented MSC-CM (hPL-MSC-CM) on skin rejuvenation characteristics. We found that the concentrations of important growth factors (VEGF, TGF-β1, and HGF) and secretory proteins for skin regeneration were significantly higher in hPL-MSC-CM than in FBS-MSC-CM. Furthermore, the capacity for inducing proliferation of human dermal fibroblast (HDF) and keratinocytes, the migration ability of HDF, extracellular matrix (ECM) production such as collagen and elastin was higher in hPL-MSC-CM than that in FBS- MSC-CM.

Conclusions

These results support the usefulness and high economic value of hPL-MSC-CM as an alternative source of FBS-MSC-CM in the cosmetic industry for skin rejuvenation.

Vasculotide restores the blood-brain barrier after focused ultrasound-induced permeability in a mouse model of Alzheimer's disease

Focused ultrasound (FUS) is used to locally and transiently induce blood-brain barrier (BBB) permeability, allowing targeted drug delivery to the brain. The purpose of the current study is to evaluate the potential of Vasculotide to accelerate the recovery of the BBB following FUS disruption in the TgCRND8 mouse model of amyloidosis, characteristic of Alzheimer's disease (AD). Accelerating the restoration of the BBB post-FUS would represent an additional safety procedure, which could be beneficial for clinical applications. Methods: TgCRND8 mice and their non-transgenic littermates were treated with Vasculotide (250 ng, intraperitoneal) every 48 hours for 3 months. BBB permeability was induced using FUS, in presence of intravenously injected microbubbles, in TgCRND8 and non-transgenic mice, and confirmed at time 0 by MRI enhancement using the contrast agent gadolinium. BBB closure was assessed at 6, 12 and 20 hours by MRI. In a separate cohort of animals, BBB closure was assessed at 24-hours post-FUS using Evans blue injected intravenously and followed by histological evaluation. Results: Chronic Vasculotide administration significantly reduces the ultra-harmonic threshold required for FUS-induced BBB permeability in the TgCRND8 mice. In addition, Vasculotide treatment led to a faster restoration of the BBB following FUS in TgCRND8 mice. BBB closure after FUS is not significantly different between TgCRND8 and non-transgenic mice. BBB permeability was assessed by gadolinium up to 20-hours post-FUS, demonstrating 87% closure in Vasculotide treated TgCRND8 mice, as opposed to 52% in PBS treated TgCRND8 mice, 58% in PBS treated non-transgenic mice, and 74% in Vasculotide treated non-transgenic mice. In both TgCRND8 mice and non-transgenic littermates the BBB was impermeable to Evans blue dye at 24-hours post-FUS. Conclusion: Vasculotide reduces the pressure required for microbubble ultra-harmonic onset for FUS-induced BBB permeability and it accelerates BBB restoration in a mouse model of amyloidosis, suggesting its potential clinical utility to promote vascular health, plasticity and repair in AD.

Treatment with an Angiopoietin-1 mimetic peptide promotes neurological recovery after stroke in diabetic rats

Aim

Vasculotide (VT), an angiopoietin‐1 mimetic peptide, exerts neuroprotective effects in type one diabetic (T1DM) rats subjected to ischemic stroke. In this study, we investigated whether delayed VT treatment improves long‐term neurological outcome after stroke in T1DM rats.

Methods

Male Wistar rats were induced with T1DM, subjected to middle cerebral artery occlusion (MCAo) model of stroke, and treated with PBS (control), 2 µg/kg VT, 3 µg/kg VT, or 5.5 µg/kg VT. VT treatment was initiated at 24 h after stroke and administered daily (i.p) for 14 days. We evaluated neurological function, lesion volume, vascular and white matter remodeling, and inflammation in the ischemic brain. In vitro, we evaluated the effects of VT on endothelial cell capillary tube formation and inflammatory responses of primary cortical neurons (PCN) and macrophages.

Results

Treatment of T1DM‐stroke with 3 µg/kg VT but not 2 µg/kg or 5.5 µg/kg significantly improves neurological function and decreases infarct volume and cell death compared to control T1DM‐stroke rats. Thus, 3 µg/kg VT dose was employed in all subsequent in vivo analysis. VT treatment significantly increases axon and myelin density, decreases demyelination, decreases white matter injury, increases number of oligodendrocytes, and increases vascular density in the ischemic border zone of T1DM stroke rats. VT treatment significantly decreases MMP9 expression and decreases the number of M1 macrophages in the ischemic brain of T1DM‐stroke rats. In vitro, VT treatment significantly decreases endothelial cell death and decreases MCP‐1, endothelin‐1, and VEGF expression under high glucose (HG) and ischemic conditions and significantly increases capillary tube formation under HG conditions when compared to non‐treated control group. VT treatment significantly decreases inflammatory factor expression such as MMP9 and MCP‐1 in macrophages subjected to LPS activation and significantly decreases IL‐1β and MMP9 expression in PCN subjected to ischemia under HG conditions.

Conclusion

Delayed VT treatment (24 h after stroke) significantly improves neurological function, promotes vascular and white matter remodeling, and decreases inflammation in the ischemic brain after stroke in T1DM rats.

Role of Angiopoietin-2 in Vascular Physiology and Pathophysiology

Angiopoietins 1–4 (Ang1–4) represent an important family of growth factors, whose activities are mediated through the tyrosine kinase receptors, Tie1 and Tie2. The best characterized are angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2). Ang1 is a potent angiogenic growth factor signaling through Tie2, whereas Ang2 was initially identified as a vascular disruptive agent with antagonistic activity through the same receptor. Recent data demonstrates that Ang2 has context-dependent agonist activities. Ang2 plays important roles in physiological processes and the deregulation of its expression is characteristic of several diseases. In this review, we summarize the activity of Ang2 on blood and lymphatic endothelial cells, its significance in human physiology and disease, and provide a current view of the molecular signaling pathways regulated by Ang2 in endothelial cells.

Angiogenic Self-Assembling Peptide Scaffolds for Functional Tissue Regeneration

Implantation of acellular biomimetic scaffolds with proangiogenic motifs may have exciting clinical utility for the treatment of ischemic pathologies such as myocardial infarction. Although direct delivery of angiogenic proteins is a possible treatment option, smaller synthetic peptide-based nanostructured alternatives are being investigated due to favorable factors, such as sustained efficacy and high-density epitope presentation of functional moieties. These peptides may be implanted in vivo at the site of ischemia, bypassing the first-pass metabolism and enabling long-term retention and sustained efficacy. Mimics of angiogenic proteins show tremendous potential for clinical use. We discuss possible approaches to integrate the functionality of such angiogenic peptide mimics into self-assembled peptide scaffolds for application in functional tissue regeneration.

The importance of the vascular endothelial barrier in the immune-inflammatory response induced by radiotherapy

Altered by ionising radiation, the vascular network is considered as a prime target to limit normal tissue damage and improve tumour control in radiotherapy (RT). Irradiation damages and/or activates endothelial cells, which then participate in the recruitment of circulating cells, especially by overexpressing cell adhesion molecules, but also by other as yet unknown mechanisms. Radiation-induced lesions are associated with infiltration of immune-inflammatory cells from the blood and/or the lymph circulation. Damaged cells from the tissues and immune-inflammatory resident cells release factors that attract cells from the circulation, leading to the restoration of tissue balance by fighting against infection, elimination of damaged cells and healing of the injured area. In normal tissues that surround the tumours, the development of an immune-inflammatory reaction in response to radiation-induced tissue injury can turn out to be chronic and deleterious for the organ concerned, potentially leading to fibrosis and/or necrosis of the irradiated area. Similarly, tumours can elicit an immune-inflammation reaction, which can be initialised and amplified by cancer therapy such as radiotherapy, although immune checkpoints often allow many cancers to be protected by inhibiting the T-cell signal. Herein, we have explored the involvement of vascular endothelium in the fate of healthy tissues and tumours undergoing radiotherapy. This review also covers current investigations that take advantage of the radiation-induced response of the vasculature to spare healthy tissue and/or target tumours better.

Topical Treatment of Skin Injury Inflicted in Mice by X-Ray Irradiation

BACKGROUND/AIMS

There is no treatment, without side effects, efficiently preventing or curing skin burns, caused by radiotherapy. A new experimental topical treatment protocol was assessed in mice receiving orthovoltage X-rays at an equivalent dose to that applied to human breast cancer patients in conventional radiotherapy.

METHODS

SKH-HR2 female hairless mice were irradiated on their dorsum with a total dose of 4,300 cGy during a 1-month period (20 fractions). The treatment group received a combination of 3 topical products, an oil-in-water cream, a gel containing Pinus halepensis bark aqueous extract, and an ointment containing olive oil extract of the marine isopod Ceratothoa oestroides. The positive control group was treated with a conventionally used commercial gel, whereas the negative control group did not receive any topical treatment. Skin alterations were evaluated by macroscopic examinations, measurements of transepidermal water loss (TEWL), melanin content, erythema intensity, hydration, and histopathology assessment.

RESULTS

Sixty days after radiation, TEWL and hydration values were abnormal and elements of acute, chronic, and granulomatous inflammation were present in all cases. The severest damage was detected in the deeper dermis. Treatment showed a comparatively beneficial effect on chronic and granulomatous inflammation while positive control was beneficial on acute inflammation.

CONCLUSION

Skin anti-inflammatory treatment was the most effective but must be applied for several months. Further preclinical studies should be conducted, assimilating a human cancer radiation therapeutic schema with the aim of optimizing skin inflammation treatment.

Vasculotide reduces pulmonary hyperpermeability in experimental pneumococcal pneumonia

BACKGROUND

Community-acquired pneumonia (CAP) is a significant cause of morbidity and mortality worldwide. Despite effective antimicrobial therapy, CAP can induce pulmonary endothelial hyperpermeability resulting in life-threatening lung failure due to an exaggerated host-pathogen interaction. Treatment of acute lung injury is mainly supportive because key elements of inflammation-induced barrier disruption remain undetermined. Angiopoietin-1 (Ang-1)-mediated Tie2 activation reduces, and the Ang-1 antagonist Ang-2 increases, inflammation and endothelial permeability in sepsis. Vasculotide (VT) is a polyethylene glycol-clustered Tie2-binding peptide that mimics the actions of Ang-1. The aim of our study was to experimentally test whether VT is capable of diminishing pneumonia-induced lung injury.

METHODS

VT binding and phosphorylation of Tie2 were analyzed using tryptophan fluorescence spectroscopy and phospho-Tie-2 enzyme-linked immunosorbent assay. Human and murine lung endothelial cells were investigated by immunofluorescence staining and electric cell-substrate impedance sensing. Pulmonary hyperpermeability was quantified in VT-pretreated, isolated, perfused, and ventilated mouse lungs stimulated with the pneumococcal exotoxin pneumolysin (PLY). Furthermore, Streptococcus pneumoniae-infected mice were therapeutically treated with VT.

RESULTS

VT showed dose-dependent binding and phosphorylation of Tie2. Pretreatment with VT protected lung endothelial cell monolayers from PLY-induced disruption. In isolated mouse lungs, VT decreased PLY-induced pulmonary permeability. Likewise, therapeutic treatment with VT of S. pneumoniae-infected mice significantly reduced pneumonia-induced hyperpermeability. However, effects by VT on the pulmonary or systemic inflammatory response were not observed.

CONCLUSIONS

VT promoted pulmonary endothelial stability and reduced lung permeability in different models of pneumococcal pneumonia. Thus, VT may provide a novel therapeutic perspective for reduction of permeability in pneumococcal pneumonia-induced lung injury.

Early biomarker for radiation-induced wounds: day one post-irradiation assessment using hemoglobin concentration measured from diffuse optical reflectance spectroscopy

Normal tissue radiation toxicities are evaluated subjectively and cannot predict the development of severe side-effects. Using a hand-held diffuse reflectance optical spectroscopy probe, we measured optical parameters in mouse skin 1-4 days after irradiation. Using a radiation toxicity model and a therapeutic mitigator described previously [BMC Cancer14, 614 (2014)], we found that hemoglobin (Hb) levels increased sharply 24 h after irradiation only in the irradiated group without the mitigator. This group also had the largest peak wound areas after 14 days. We conclude that increased Hb one day after skin irradiation predicts the severity of the subsequent irradiation-induced wound.

Vasculotide, an Angiopoietin-1 mimetic, ameliorates several features of experimental atopic dermatitis-like disease

Background

Earlier studies by our group have demonstrated that a transgenic animal engineered to express Tie2 under the control of the Tie2 promoter produced animals with a scaly skin phenotype that recapitulated many of the hallmarks of atopic dermatitis (AT-Derm). To test the hypothesis that this model of AT-Derm is driven by dysregulated Tie2-signalling, we have bred AT-Derm transgenic (TG) animals with TG-animals engineered to overexpress Angiopoietin-1 or -2, the cognate Tie2 ligands. These two ligands act to antagonize one another in a context-dependent manner. To further evaluate the role of Ang1-driven-Tie2 signalling, we examined the ability of Vasculotide, an Ang1-mimetic, to modulate the AT-Derm phenotype.

Results

AT-Derm+Ang2 animals exhibited an accentuated phenotype, whereas AT-Derm+Ang1 presented with a markedly reduced skin disease, similarly VT-treated AT-Derm animals present with a clear decrease in the skin phenotype. Moreover, a decrease in several important inflammatory cytokines and a decrease in the number of eosinophils was noted in VT-treated animals. Bone marrow differentiation in the presence of VT produced fewer CFU-G colonies, further supporting a role for Tie2-signalling in eosinophil development. Importantly, we demonstrate activation of Tie2, the VT-target, in lung tissue from naïve animals treated with increasing amounts of VT.

Conclusions

The AT-Derm phenotype in these animals is driven through dysregulation of Tie2 receptor signalling and is augmented by supplemental Ang2-dependent stimulation. Overexpression of Ang1 or treatment with VT produced a similar amelioration of the phenotype supporting the contention that VT and Ang1 have a similar mechanism of action on the Tie2 receptor and can both counteract the signalling driven by Ang2. Our results also support a possible role for Tie2-signalling in the development of eosinophilic diseases and that activation of Tie2 may directly or indirectly modulate the differentiation of eosinophils, which express Tie2. In summary, these data support the hypothesis that this AT-Derm mouse model is driven by dysregulation of the Tie2 signalling pathway and increased Ang2 levels can aggravate it, whereas it can be reversed by either Ang1-overexpression or VT treatment. Moreover, our data supports the contention that VT acts as an Angiopoietin-1 mimetic and may provide a novel entry point for Tie2-agonist-based therapies for atopic diseases.

Diffuse Optical Spectroscopy for the Quantitative Assessment of Acute Ionizing Radiation Induced Skin Toxicity Using a Mouse Model

Acute skin toxicities from ionizing radiation (IR) are a common side effect from therapeutic courses of external beam radiation therapy (RT) and negatively impact patient quality of life and long term survival. Advances in the understanding of the biological pathways associated with normal tissue toxicities have allowed for the development of interventional drugs, however, current response studies are limited by a lack of quantitative metrics for assessing the severity of skin reactions. Here we present a diffuse optical spectroscopic (DOS) approach that provides quantitative optical biomarkers of skin response to radiation. We describe the instrumentation design of the DOS system as well as the inversion algorithm for extracting the optical parameters. Finally, to demonstrate clinical utility, we present representative data from a pre-clinical mouse model of radiation induced erythema and compare the results with a commonly employed visual scoring. The described DOS method offers an objective, high through-put evaluation of skin toxicity via functional response that is translatable to the clinical setting.

Vasculotide reduces endothelial permeability and tumor cell extravasation in the absence of binding to or agonistic activation of Tie2

Angiopoietin-1 (Ang1) activation of Tie2 receptors on endothelial cells (ECs) reduces adhesion by tumor cells (TCs) and limits junctional permeability to TC diapedesis. We hypothesized that systemic therapy with Vasculotide (VT)—a purported Ang1 mimetic, Tie2 agonist—can reduce the extravasation of potentially metastatic circulating TCs by similarly stabilizing the host vasculature. In vitro, VT and Ang1 treatments impeded endothelial hypermeability and the transendothelial migration of MDA-MB-231•LM2-4 (breast), HT29 (colon), or SN12 (renal) cancer cells to varying degrees. In mice, VT treatment inhibited the transit of TCs through the pulmonary endothelium, but not the hepatic or lymphatic endothelium. In the in vivo LM2-4 model, VT monotherapy had no effect on primary tumors, but significantly delayed distant metastatic dissemination to the lungs. In the post-surgical adjuvant treatment setting, VT therapeutically complemented sunitinib therapy, an anti-angiogenic tyrosine kinase inhibitor which limited the local growth of residual disease. Unexpectedly, detailed investigations into the putative mechanism of action of VT revealed no evidence of Tie2 agonism or Tie2 binding; alternative mechanisms have yet to be determined.

The Synthetic Tie2 Agonist Peptide Vasculotide Protects Renal Vascular Barrier Function In Experimental Acute Kidney Injury

Microvascular barrier dysfunction plays a major role in the pathophysiology of acute kidney injury (AKI). Angiopoietin-1, the natural agonist ligand for the endothelial-specific Tie2 receptor, is a non-redundant endothelial survival and vascular stabilization factor. Here we evaluate the efficacy of a polyethylene glycol-clustered Tie2 agonist peptide, vasculotide (VT), to protect against endothelial-cell activation with subsequent microvascular dysfunction in a murine model of ischemic AKI. Renal ischemia reperfusion injury (IRI) was induced by clamping of the renal arteries for 35 minutes. Mice were treated with VT or PEGylated cysteine before IRI. Sham-operated animals served as time-matched controls. Treatment with VT significantly reduced transcapillary albumin flux and renal tissue edema after IRI. The protective effects of VT were associated with activation of Tie2 and stabilization of its downstream effector, VE-cadherin in renal vasculature. VT abolished the decline in renal tissue blood flow, attenuated the increase of serum creatinine and blood urea nitrogen after IRI, improved recovery of renal function and markedly reduced mortality compared to PEG [HR 0.14 (95% CI 0.05-0.78) P < 0.05]. VT is inexpensive to produce, chemically stable and unrelated to any Tie2 ligands. Thus, VT may represent a novel therapy to prevent AKI in patients.

Fibrinogen-Related Proteins in Tissue Repair: How a Unique Domain with a Common Structure Controls Diverse Aspects of Wound Healing

Significance: Fibrinogen-related proteins (FRePs) comprise an intriguing collection of extracellular molecules, each containing a conserved fibrinogen-like globe (FBG). This group includes the eponymous fibrinogen as well as the tenascin, angiopoietin, and ficolin families. Many of these proteins are upregulated during tissue repair and exhibit diverse roles during wound healing. Recent Advances: An increasing body of evidence highlights the specific expression of a number of FRePs following tissue injury and infection. Upon induction, each FReP uses its FBG domain to mediate quite distinct effects that contribute to different stages of tissue repair, such as driving coagulation, pathogen detection, inflammation, angiogenesis, and tissue remodeling. Critical Issues: Despite a high degree of homology among FRePs, each contains unique sequences that enable their diversification of function. Comparative analysis of the structure and function of FRePs and precise mapping of regions that interact with a variety of ligands has started to reveal the underlying molecular mechanisms by which these proteins play very different roles using their common domain. Future Directions: Fibrinogen has long been used in the clinic as a synthetic matrix serving as a scaffold or a delivery system to aid tissue repair. Novel therapeutic strategies are now emerging that harness the use of other FRePs to improve wound healing outcomes. As we learn more about the underlying mechanisms by which each FReP contributes to the repair response, specific blockade, or indeed potentiation, of their function offers real potential to enable regulation of distinct processes during pathological wound healing.

Endothelial perturbations and therapeutic strategies in normal tissue radiation damage

Most cancer patients are treated with radiotherapy, but the treatment can also damage the surrounding normal tissue. Radiotherapy side-effects diminish patients’ quality of life, yet effective biological interventions for normal tissue damage are lacking. Protecting microvascular endothelial cells from the effects of irradiation is emerging as a targeted damage-reduction strategy. We illustrate the concept of the microvasculature as a mediator of overall normal tissue radiation toxicity through cell death, vascular inflammation (hemodynamic and molecular changes) and a change in functional capacity. Endothelial cell targeted therapies that protect against such endothelial cell perturbations and the development of acute normal tissue damage are mostly under preclinical development. Since acute radiation toxicity is a common clinical problem in cutaneous, gastrointestinal and mucosal tissues, we also focus on damage in these tissues.