Topical Administration of a Novel Acetylated Tetrapeptide Suppresses Vascular Permeability and Immune Responses and Alleviates Atopic Dermatitis in a Murine Model.

Although the pathogenesis of atopic dermatitis (AD) remains to be fully deciphered, skin barrier abnormality and immune dysregulation are known to be involved. Recently, the vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) system has also been implicated in the pathogenesis of this multifactorial chronic inflammatory skin disorder. Previously, we showed that a novel tetrapeptide, N-acetyl-Arg-Leu-Tyr-Glu (Ac-RLYE), inhibits angiogenesis and vascular permeability effectively by selectively antagonizing VEGFR-2. The current study aimed to investigate the pharmacological effect of Ac-RLYE on AD in vitro and in vivo. The in vitro experiments demonstrated that Ac-RLYE inhibited VEGF-induced vascular permeability in endothelial cells. Moreover, in an in vivo animal model of AD, Ac-RLYE relieved AD-like symptoms such as ear thickness and dermatitis severity scores and infiltration of immune cells, including mast cells and eosinophils. Ac-RLYE inhibited IgE secretion, restored the skin barrier protein filaggrin level, and markedly downregulated gene expression of AD-related Th1, Th2, and Th17 cytokines. Collectively, these findings suggest that Ac-RLYE would be useful for the treatment of AD and associated inflammatory skin disorders.

In Vivo Efficacy of Imatinib Mesylate, a Tyrosine Kinase Inhibitor, in the Treatment of Chemically Induced Dry Eye in Animal Models.

Purpose: Dry eye disease (DED) is a multifactorial disorder of the tears and ocular surface accompanied by ocular discomfort, visual disturbance, tear film instability, and ocular surface inflammation. In the present study, we evaluated the efficacy of the tyrosine kinase inhibitor imatinib mesylate for the treatment of DED. Methods: Experimental models of DED were generated in Sprague Dawley rats using a combination of benzalkonium chloride (BAC) with atropine sulfate and in New Zealand White rabbits using BAC. The animals were treated twice daily with eye drops of vehicle, imatinib (0.01%-0.3%), or a positive control (Restasis). The improvement in DED due to imatinib was assessed by staining with fluorescein, lissamine green, impression cytology, and histological analysis. In addition, immunofluorescence staining was performed at the end of the study to evaluate the inflammatory response in the ocular surface. Results: Topical application of imatinib significantly reduced ocular surface damage compared with vehicle-treated animals. Imatinib restored the morphology and structure of the conjunctival epithelium and reduced the recruitment of immune cells in the corneal epithelium. Furthermore, imatinib significantly reduced the impression cytology score, thus demonstrating that imatinib prevents the loss of goblet cells in DED animal models. The therapeutic efficacy of imatinib was similar to or better than that of cyclosporine treatment. Conclusions: In this study, we provide an animal in vivo proof of concept of the therapeutic potential of imatinib for the treatment of DED. Translational Relevance: With this study we show the possibility of developing imatinib as a new ophthalmic drop to treat DED.

Therapeutic Efficacy of a Novel Acetylated Tetrapeptide in Animal Models of Age-Related Macular Degeneration.

It has been shown previously that a novel tetrapeptide, Arg-Leu-Tyr-Glu (RLYE), derived from human plasminogen inhibits vascular endothelial growth factor (VEGF)-induced angiogenesis, suppresses choroidal neovascularization in mice by an inhibition of VEGF receptor-2 (VEGFR-2) specific signaling pathway. In this study, we report that a modified tetrapeptide (Ac-RLYE) showed improved anti-choroidal neovascularization (CNV) efficacy in a number of animal models of neovascular age-related macular degeneration (AMD) which include rat, rabbit, and minipig. The preventive and therapeutic in vivo efficacy of Ac-RLYE via following intravitreal administration was determined to be either similar or superior to that of ranibizumab and aflibercept. Assessment of the intraocular pharmacokinetic and toxicokinetic properties of Ac-RLYE in rabbits demonstrated that it rapidly reached the retina with minimal systemic exposure after a single intravitreal dose, and it did not accumulate in plasma during repetitive dosing (bi-weekly for 14 weeks). Our results suggested that Ac-RLYE has a great potential for an alternative therapeutics for neovascular (wet) AMD. Since the amino acids in human VEGFR-2 targeted by Ac-RLYE are conserved among the animals employed in this study, the therapeutic efficacies of Ac-RLYE evaluated in those animals are predicted to be observed in human patients suffering from retinal degenerative diseases.

Local Delivery of Gemcitabine Inhibits Pancreatic and Cholangiocarcinoma Tumor Growth by Promoting Epidermal Growth Factor Receptor Degradation.

Gemcitabine is clinically used to treat certain types of cancers, including pancreatic and biliary cancer. We investigated the signal transduction pathways underlying the local antitumor effects of gemcitabine-eluting membranes (GEMs) implanted in pancreatic/biliary tumor-bearing nude mice. Here, we report that GEMs increased the E3 ubiquitin ligase c-CBL protein level, leading to degradation of epidermal growth factor receptor (EGFR) in SCK and PANC-1 cells. GEMs decreased the RAS and PI3K protein levels, leading to a reduction in the protein levels of active forms of downstream signaling molecules, including PDK, AKT, and GSK3ß. GEM reduced proliferation of cancer cells by upregulating cell cycle arrest proteins, particularly p53 and p21, and downregulating cyclin D1 and cyclin B. Moreover, GEMs reduced the levels of proangiogenic factors, including VEGF, VEGFR2, CD31, and HIF-1α, and inhibited tumor cell migration and invasion by inducing the expression of E-cadherin and reducing that of N-cadherin, snail, and vimentin. We demonstrated that local delivery of gemcitabine using GEM implants inhibited tumor cell growth by promoting c-CBL-mediated degradation of EGFR and inhibiting the proliferation, angiogenesis, and epithelial-mesenchymal transition of pancreatic/biliary tumors. Use of gemcitabine-eluting stents can improve stent patency by inhibiting the ingrowth of malignant biliary obstructions.

N-Terminal Modification of the Tetrapeptide Arg-Leu-Tyr-Glu, a Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) Antagonist, Improves Antitumor Activity by Increasing its Stability against Serum Peptidases.

The tetrapeptide Arg-Leu-Tyr-Glu (RLYE), a vascular endothelial growth factor (VEGF) receptor-2 antagonist, has been used previously either alone or in combination with chemotherapeutic drugs for treating colorectal cancer in a mouse model. We analyzed the half-life of the peptide and found that because of degradation by aminopeptidases B and N, it had a short half-life of 1.2 hours in the serum. Therefore, to increase the stability and potency of the peptide, we designed the modified peptide, N-terminally acetylated RLYE (Ac-RLYE), which had a strongly stabilized half-life of 8.8 hours in serum compared with the original parent peptide. The IC50 value of Ac-RLYE for VEGF-A-induced endothelial cell migration decreased to approximately 37.1 pM from 89.1 pM for the parent peptide. Using a mouse xenograft tumor model, we demonstrated that Ac-RLYE was more potent than RLYE in inhibiting tumor angiogenesis and growth, improving vascular integrity and normalization through enhanced endothelial cell junctions and pericyte coverage of the tumor vasculature, and impeding the infiltration of macrophages into tumor and their polarization to the M2 phenotype. Furthermore, combined treatment of Ac-RLYE and irinotecan exhibited synergistic effects on M1-like macrophage activation and apoptosis and growth inhibition of tumor cells. These findings provide evidence that the N-terminal acetylation augments the therapeutic effect of RLYE in solid tumors via inhibition of tumor angiogenesis, improvement of tumor vessel integrity and normalization, and enhancement of the livery and efficacy of the coadministered chemotherapeutic drugs. SIGNIFICANCE STATEMENT: The results of this study demonstrate that the N-terminal acetylation of the tetrapeptide RLYE (Ac-RLYE), a novel vascular endothelial growth factor receptor-2 (VEGFR-2) inhibitor, significantly improves its serum stability, antiangiogenic activity, and vascular normalizing potency, resulting in enhanced therapeutic effect on solid tumors. Furthermore, the combined treatment of Ac-RLYE with the chemotherapeutic drug, irinotecan, synergistically enhanced its antitumor efficacy by improving the perfusion and delivery of the drug into the tumors and stimulating the conversion of the tumor-associated macrophages to an immunostimulatory M1-like antitumor phenotype.

Arg-Leu-Tyr-Glu Suppresses Retinal Endothelial Permeability and Choroidal Neovascularization by Inhibiting the VEGF Receptor 2 Signaling Pathway.

Vascular endothelial growth factor (VEGF) plays a pivotal role in pathologic ocular neovascularization and vascular leakage via activation of VEGF receptor 2 (VEGFR2). This study was undertaken to evaluate the therapeutic mechanisms and effects of the tetrapeptide Arg-Leu-Tyr-Glu (RLYE), a VEGFR2 inhibitor, in the development of vascular permeability and choroidal neovascularization (CNV). In cultured human retinal microvascular endothelial cells (HRMECs), treatment with RLYE blocked VEGF-A-induced phosphorylation of VEGFR2, Akt, ERK, and endothelial nitric oxide synthase (eNOS), leading to suppression of VEGFA-mediated hyper-production of NO. Treatment with RLYE also inhibited VEGF-A-stimulated angiogenic processes (migration, proliferation, and tube formation) and the hyperpermeability of HRMECs, in addition to attenuating VEGF-A-induced angiogenesis and vascular permeability in mice. The anti-vascular permeability activity of RLYE was correlated with enhanced stability and positioning of the junction proteins VE-cadherin, ß-catenin, claudin-5, and ZO-1, critical components of the cortical actin ring structure and retinal endothelial barrier, at the boundary between HRMECs stimulated with VEGF-A. Furthermore, intravitreally injected RLYE bound to retinal microvascular endothelium and inhibited laser-induced CNV in mice. These findings suggest that RLYE has potential as a therapeutic drug for the treatment of CNV by preventing VEGFR2-mediated vascular leakage and angiogenesis.

Arg-Leu-Tyr-Glu tetrapeptide inhibits tumor progression by suppressing angiogenesis and vascular permeability via VEGF receptor-2 antagonism.

The tetrapeptide Arg-Leu-Tyr-Glu (RLYE) is known to inhibit vascular endothelial growth factor-A (VEGF-A)-induced angiogenesis in vitro. Herein, we examined its underlying mechanism and antitumor activity associated with vascular remodeling. RLYE inhibited VEGF-A-induced angiogenesis in a mouse model and suppressed VEGF-A-induced angiogenic signal cascades in human endothelial cells. However, RLYE showed no inhibitory effect on VEGF-A-induced proliferation and migration of multiple myeloma cells expressing VEGF receptor (VEGFR)-1, but not VEGFR-2. In addition, RLYE showed no inhibitory effect on angiogenic activities induced by VEGF-B, basic fibroblast growth factor, epithermal growth factor, sphingosine-1-phosphate, and placental growth factor. RLYE bound specifically to VEGFR-2 at the VEGF-A binding site, thereby blocking VEGF-A-VEGFR-2 binding and VEGF-A-induced VEGFR-2 internalization. The RLYE peptide inhibited tumor growth and metastasis via suppression of tumor angiogenesis in tumor-bearing mice. Moreover, RLYE showed a synergistic effect of the cytotoxic agent irinotecan on tumor cell apoptosis and tumor progression via tumor vessel normalization due to stabilization of VE-cadherin-mediated adherens junction, improvement of pericyte coverage, and inhibition of vascular leakage in tumors. Our results suggest that RLYE can be used as an antiangiogenic and tumor blood vessel remodeling agent for inhibition of tumor growth and metastasis by antagonizing VEGFR-2, with the synergistic anti-cancer effect via enhancement of drug delivery and therapeutic efficacy.

Carbon monoxide stimulates astrocytic mitochondrial biogenesis via L-type Ca2+ channel-mediated PGC-1α/ERRα activation.

Carbon monoxide (CO), derived by the enzymatic reaction of heme oxygenase (HO), is a cellular regulator of energy metabolism and cytoprotection; however, its underlying mechanism has not been clearly elucidated. Astrocytes pre-exposed to the CO-releasing compound CORM-2 increased mitochondrial biogenesis, mitochondrial electron transport components (cytochrome c, Cyt c; cytochrome c oxidase subunit 2, COX2), and ATP synthesis. The increased mitochondrial function was correlated with activation of AMP-activated protein kinase α and upregulation of HO-1, peroxisome proliferators-activated receptor γ-coactivator-1α (PGC-1α), and estrogen-related receptor α (ERRα). These events elicited by CORM-2 were suppressed by Ca2+ chelators, a HO inhibitor, and an L-type Ca2+ channel blocker, but not other Ca2+ channel inhibitors. Among the HO byproducts, combined CORM-2 and bilirubin treatment effectively increased PGC-1α, Cyt c and COX2 expression, mitochondrial biogenesis, and ATP synthesis, and these increases were blocked by Ca2+ chelators. Moreover, cerebral ischemia significantly increased HO-1, PGC-1α, and ERRα levels, subsequently increasing Cyt c and COX2 expression, in wild-type mice, compared with HO-1+/- mice. These results suggest that HO-1-derived CO enhances mitochondrial biogenesis in astrocytes by activating L-type Ca2+ channel-mediated PGC-1α/ERRα axis, leading to maintenance of astrocyte function and neuroprotection/recovery against damage of brain function.

The tetrapeptide Arg-Leu-Tyr-Glu inhibits VEGF-induced angiogenesis.

Kringle 5, derived from plasminogen, is highly capable of inhibiting angiogenesis. Here, we have designed and synthesized 10 tetrapeptides, based on the amino acid properties of the core tetrapeptide Lys-Leu-Tyr-Asp (KLYD) originating from anti-angiogenic kringle 5 of human plasminogen. Of these, Arg-Leu-Tyr-Glu (RLYE) effectively inhibited vascular endothelial growth factor (VEGF)-induced endothelial cell proliferation, migration and tube formation, with an IC50 of 0.06-0.08 nM, which was about ten-fold lower than that of the control peptide KLYD (0.79 nM), as well as suppressed developmental angiogenesis in a zebrafish model. Furthermore, this peptide effectively inhibited the cellular events that precede angiogenesis, such as ERK and eNOS phosphorylation and nitric oxide production, in endothelial cells stimulated with VEGF. Collectively, these data demonstrate that RLYE is a potent anti-angiogenic peptide that targets the VEGF signaling pathway.

Molecular mechanism of local drug delivery with Paclitaxel-eluting membranes in biliary and pancreatic cancer: new application for an old drug.

Implantation of self-expanding metal stents (SEMS) is palliation for patients suffering from inoperable malignant obstructions associated with biliary and pancreatic cancers. Chemotherapeutic agent-eluting stents have been developed because SEMS are susceptible to occlusion by tumor in-growth. We reported recently that paclitaxel-eluting SEMS provide enhanced local drug delivery in an animal model. However, little is known about the molecular mechanisms by which paclitaxel-eluting stents attenuate tumor growth. We investigated the signal transduction pathways underlying the antiproliferative effects of a paclitaxel-eluting membrane (PEM) implanted in pancreatic/cholangiocarcinoma tumor bearing nude mice. Molecular and cellular alterations were analyzed in the PEM-implanted pancreatic/cholangiocarcinoma xenograft tumors by Western blot, immunoprecipitation, and immunofluorescence. The quantities of paclitaxel released into the tumor and plasma were determined by liquid chromatography-tandem mass spectroscopy. Paclitaxel from the PEM and its diffusion into the tumor inhibited angiogenesis, which involved suppression of mammalian target of rapamycin (mTOR) through regulation of hypoxia inducible factor (HIF-1) and increased apoptosis. Moreover, implantation of the PEM inhibited tumor-stromal interaction-related expression of proteins such as CD44, SPARC, matrix metalloproteinase-2, and vimentin. Local delivery of paclitaxel from a PEM inhibited growth of pancreatic/cholangiocarcinoma tumors in nude mice by suppressing angiogenesis via the mTOR and inducing apoptosis signal pathway.

Hypoxia-mediated retinal neovascularization and vascular leakage in diabetic retina is suppressed by HIF-1α destabilization by SH-1242 and SH-1280, novel hsp90 inhibitors.

In diabetic retinopathy (DR), visual deterioration is related with retinal neovascularization and vascular hyperpermeability. Anti-vascular endothelial growth factor (VEGF) agents are currently utilized to suppress retinal neovascularization and macular edema (ME); however, there are still concerns on the widespread use of them because VEGF is a trophic factor for neuronal and endothelial cells in the retina. As an alternative treatment strategy for DR, it is logical to address hypoxia-related molecules to treat DR because the retina is in relative hypoxia as DR progresses. In this study, we demonstrate that destabilization of hypoxia-inducible factor-1α (HIF-1α) by SH-1242 and SH-1280, novel heat shock protein 90 (hsp90) inhibitors, leads to suppression of hypoxia-mediated retinal neovascularization and vascular leakage in diabetic retina. In vitro experiments showed that these inhibitors inhibited hypoxia-induced upregulation of target genes of HIF-1α and further secretion of VEGF. Furthermore, these inhibitors effectively suppressed expression of target genes of HIF-1α including vegfa in the retina of oxygen-induced retinopathy (OIR) mice. Interestingly, despite hsp90 inhibition, these inhibitors do not induce definite toxicity at the level of gene expression, cellular viability, and histologic integrity. We suggest that SH-1242 and SH-1280 can be utilized in the treatment of DR, as an alternative treatment of direct VEGF inhibition. Key message: SH-1242 and SH-1280 are novel hsp90 inhibitors similar to deguelin. HIF-1α destabilization by hsp90 inhibition leads to anti-angiogenic effects. Despite hsp90 inhibition, both inhibitors do not induce definite toxicity. HIF-1α modulation can be a safer therapeutic option than direct VEGF inhibition.

Functional dissection of Nrf2-dependent phase II genes in vascular inflammation and endotoxic injury using Keap1 siRNA.

Keap1 is a cytoplasmic repressor of the transcription factor Nrf2, and its degradation induces Nrf2 activation, leading to upregulation of antioxidant phase II genes. We investigated the roles of phase II genes in vascular inflammation and septic injury using Keap1 siRNA and elucidated its underlying mechanism. Selective knockdown of Keap1 with siRNA promoted Nrf2-dependent expression of phase II genes in endothelial cells, such as heme oxygenase-1 (HO-1), glutamate-cysteine ligase (GCL), and peroxiredoxin-1 (Prx1), resulting in the elevation of cellular glutathione levels and suppression of tumor necrosis factor (TNF)-α-induced intracellular H(2)O(2) accumulation. Keap1 knockdown inhibited TNF-α-induced expression of intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) by suppressing NF-κB activation via inhibition of its upstream modulators, Akt, NIK, and IKK, resulting in the elevation of monocyte adhesion to endothelial cells. Importantly, these events were reversed by HO-1 and GCL inhibitors and Prx1-specific siRNA. Keap1 knockdown also inhibited endotoxin-induced expression of inducible nitric oxide synthase (iNOS) and TNF-α by upregulating HO-1, GCL, and Prx1 expression in macrophages. Moreover, in vivo Keap1 knockdown increased the expression of phase II genes and suppressed the expression of ICAM-1, VCAM-1, iNOS, and TNF-α in an endotoxemic mouse model, resulting in significant protection against liver and lung injuries and lethality. Our results indicate that Keap1 knockdown prevents NF-κB-mediated vascular inflammation and endotoxic shock by suppressing NF-κB-mediated inflammatory gene expression via upregulation of Nrf2-mediated antioxidant genes. Thus, siRNA targeting Keap1 may provide a new therapeutic approach for inflammation-associated vascular diseases and sepsis.

Syringaresinol causes vasorelaxation by elevating nitric oxide production through the phosphorylation and dimerization of endothelial nitric oxide synthase.

Nitric oxide (NO) produced by endothelial NO synthase (eNOS) plays an important role in vascular functions, including vasorelaxation. We here investigated the pharmacological effect of the natural product syringaresinol on vascular relaxation and eNOS-mediated NO production as well as its underlying biochemical mechanism in endothelial cells. Treatment of aortic rings from wild type, but not eNOS(-/-) mice, with syringaresinol induced endothelium-dependent relaxation, which was abolished by addition of the NOS inhibitor N(G)-monomethyl-L-arginine. Treatment of human endothelial cells and mouse aortic rings with syringaresinol increased NO production, which was correlated with eNOS phosphorylation via the activation of Akt and AMP kinase (AMPK) as well as elevation of intracellular Ca(2+) levels. A phospholipase C (PLC) inhibitor blocked the increases in intracellular Ca(2+) levels, AMPK-dependent eNOS phosphorylation, and NO production, but not Akt activation, in syringaresinol- treated endothelial cells. Syringaresinol-induced AMPK activation was inhibited by co-treatment with PLC inhibitor, Ca(2+) chelator, calmodulin antagonist, and CaMKKß siRNA. This compound also increased eNOS dimerization, which was inhibited by a PLC inhibitor and a Ca(2+)-chelator. The chemicals that inhibit eNOS phosphorylation and dimerization attenuated vasorelaxation and cGMP production. These results suggest that syringaresinol induces vasorelaxation by enhancing NO production in endothelial cells via two distinct mechanisms, phosphatidylinositol 3-kinase/Akt- and PLC/Ca(2+)/CaMKKß-dependent eNOS phosphorylation and Ca(2+)-dependent eNOS dimerization.

Extracellular taurine induces angiogenesis by activating ERK-, Akt-, and FAK-dependent signal pathways.

Taurine, a non essential sulfur-containing amino acid, plays a critical role in cardiovascular functions. We here examined the effect of taurine on angiogenesis and its underlying signal pathway. Taurine treatment increased angiogenesis in vitro and in vivo, which was followed by activation of the phosphatidylinositol 3-kinase (PI3K)/Akt, MEK/ERK, and Src/FAK signaling pathways. Further, taurine promoted endothelial cell cycle progression to the S and G2/M phases by up-regulating the positive cell cycle proteins, particularly cyclins D1 and B, as well as down-regulating the negative cell cycle proteins, p53 and p21(WAF1/CIP1), resulting in Rb phosphorylation. This angiogenic event was inhibited by inhibitors of PI3K and MEK. In addition, a PI3K inhibitor blocked the activation of Akt and ERK, while Akt knockdown did not affect taurine-induced ERK activation, indicating that PI3K is an upstream mediator of both MEK and Akt. Taurine-induced endothelial cell migration was suppressed by Src inhibitor, but not by other inhibitors, suggesting that the increase in cell migration is regulated by Src-dependent pathway. Moreover, inhibition of cellular taurine uptake by ß-alanine and taurine transporter knockdown promoted taurine-induced cell proliferation, ERK and Akt activation, and in vivo angiogenesis, suggesting that extracellular taurine induces angiogenesis. However, taurine did not induce vascular inflammation and permeability in vitro and in vivo. These data demonstrate that extracellular taurine promotes angiogenesis by Akt- and ERK-dependent cell cycle progression and Src/FAK-mediated cell migration without inducing vascular inflammation, indicating that it is potential use for the treatment of vascular dysfunction-associated human diseases.