Receptor activity-modifying proteins of adrenomedullin (RAMP2/3): Roles in the pathogenesis of ARDS.

Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition characterized by widespread inflammation and pulmonary edema. Adrenomedullin (AM), a bioactive peptide with various functions, is expected to be applied in treating ARDS. Its functions are regulated primarily by two receptor activity-modifying proteins, RAMP2 and RAMP3, which bind to the AM receptor calcitonin receptor-like receptor (CLR). However, the roles of RAMP2 and RAMP3 in ARDS remain unclear. We generated a mouse model of ARDS via intratracheal administration of lipopolysaccharide (LPS), and analyzed the pathophysiological significance of RAMP2 and RAMP3. RAMP2 expression declined with LPS administration, whereas RAMP3 expression increased at low doses and decreased at high doses of LPS. After LPS administration, drug-inducible vascular endothelial cell-specific RAMP2 knockout mice (DI-E-RAMP2-/-) showed reduced survival, increased lung weight, and had more apoptotic cells in the lungs. DI-E-RAMP2-/- mice exhibited reduced expression of Epac1 (which regulates vascular endothelial cell barrier function), while RAMP3 was upregulated in compensation. In contrast, after LPS administration, RAMP3-/- mice showed no significant changes in survival, lung weight, or lung pathology, although they exhibited significant downregulation of iNOS, TNF-α, and NLRP3 during the later stages of inflammation. Based on transcriptomic analysis, RAMP2 contributed more to the circulation-regulating effects of AM, whereas RAMP3 contributed more to its inflammation-regulating effects. These findings indicate that, while both RAMP2 and RAMP3 participate in ARDS pathogenesis, their functions differ distinctly. Further elucidation of the pathophysiological significance and functional differences between RAMP2 and RAMP3 is critical for the future therapeutic application of AM in ARDS.

Role of Adrenomedullin 2/Intermedin in the Pathogenesis of Neovascular Age-Related Macular Degeneration.

Adrenomedullin 2 (AM2; also known as intermedin) is a member of the adrenomedullin (AM) peptide family. Similarly to AM, AM2 partakes in a variety of physiological activities. AM2 has been reported to exert protective effects on various organ disorders; however, its significance in the eye is unknown. We investigated the role of AM2 in ocular diseases. The receptor system of AM2 was expressed more abundantly in the choroid than in the retina. In an oxygen-induced retinopathy model, physiological and pathologic retinal angiogenesis did not differ between AM2-knockout (AM2-/-) and wild-type mice. In contrast, in laser-induced choroidal neovascularization, a model of neovascular age-related macular degeneration, AM2-/- mice had enlarged and leakier choroidal neovascularization lesions, with exacerbated subretinal fibrosis and macrophage infiltration. Contrary to this, exogenous administration of AM2 ameliorated the laser-induced choroidal neovascularization-associated pathology and suppressed gene expression associated with inflammation, fibrosis, and oxidative stress, including that of VEGF-A, VEGFR-2, CD68, CTGF, and p22-phox. The stimulation of human adult retinal pigment epithelial (ARPE) cell line 19 cells with TGF-ß2 and TNF-α induced epithelial-to-mesenchymal transition (EMT), whereas AM2 expression was also elevated. The induction of EMT was suppressed when the ARPE-19 cells were pretreated with AM2. A transcriptome analysis identified 15 genes, including mesenchyme homeobox 2 (Meox2), whose expression was significantly altered in the AM2-treated group compared with that in the control group. The expression of Meox2, a transcription factor that inhibits inflammation and fibrosis, was enhanced by AM2 treatment and attenuated by endogenous AM2 knockout in the early phase after laser irradiation. The AM2 treatment of endothelial cells inhibited endothelial to mesenchymal transition and NF-κB activation; however, this effect tended to be canceled following Meox2 gene knockdown. These results indicate that AM2 suppresses the neovascular age-related macular degeneration-related pathologies partially via the upregulation of Meox2. Thus, AM2 may be a promising therapeutic target for ocular vascular diseases.

Receptor Activity Modifying Protein RAMP Sub-Isoforms and Their Functional Differentiation, Which Regulates Functional Diversity of Adrenomedullin.

AM knockout (AM-/-) and RAMP2 knockout (RAMP2-/-) proved lethal for mice due to impaired embryonic vascular development. Although most vascular endothelial cell-specific RAMP2 knockout (E-RAMP2-/-) mice also died during the perinatal period, a few E-RAMP2-/- mice reached adulthood. Adult E-RAMP2-/- mice developed spontaneous organ damage associated with vascular injury. In contrast, adult RAMP3 knockout (RAMP3-/-) mice showed exacerbated postoperative lymphedema with abnormal lymphatic drainage. Thus, RAMP2 is essential for vascular development and homeostasis and RAMP3 is essential for lymphatic vessel function. Cardiac myocyte-specific RAMP2 knockout mice showed early onset of heart failure as well as abnormal mitochondrial morphology and function, whereas RAMP3-/- mice exhibited abnormal cardiac lymphatics and a delayed onset of heart failure. Thus, RAMP2 is essential for maintaining cardiac mitochondrial function, while RAMP3 is essential for cardiac lymphangiogenesis. Transplantation of cancer cells into drug-inducible vascular endothelial cell-specific RAMP2 knockout mice resulted in enhanced metastasis to distant organs, whereas metastasis was suppressed in RAMP3-/- mice. RAMP2 suppresses cancer metastasis by maintaining vascular homeostasis and inhibiting vascular inflammation and pre-metastatic niche formation, while RAMP3 promotes cancer metastasis via malignant transformation of cancer-associated fibroblasts. Focusing on the diverse physiological functions of AM and the functional differentiation of RAMP2 and RAMP3 may lead to the development of novel therapeutic strategies.

Adrenomedullin Ameliorates Pulmonary Fibrosis by Regulating TGF-ß-Smads Signaling and Myofibroblast Differentiation.

Pulmonary fibrosis is an irreversible, potentially fatal disease. Adrenomedullin (AM) is a multifunctional peptide whose activity is regulated by receptor activity-modifying protein 2 (RAMP2). In the present study, we used the bleomycin (BLM)-induced mouse pulmonary fibrosis model to investigate the pathophysiological significance of the AM-RAMP2 system in the lung. In heterozygous AM knockout mice (AM+/-), hydroxyproline content and Ashcroft scores reflecting the fibrosis severity were significantly higher than in wild-type mice (WT). During the acute phase after BLM administration, FACS analysis showed significant increases in eosinophil, monocyte, and neutrophil infiltration into the lungs of AM+/-. During the chronic phase, fibrosis-related molecules were upregulated in AM+/-. Notably, nearly identical changes were observed in RAMP2+/-. AM administration reduced fibrosis severity. In the lungs of BLM-administered AM+/-, the activation level of Smad3, a receptor-activated Smad, was higher than in WT. In addition, Smad7, an antagonistic Smad, was downregulated and microRNA-21, which targets Smad7, was upregulated compared to WT. Isolated AM+/- lung fibroblasts showed less proliferation and migration capacity than WT fibroblasts. Stimulation with TGF-ß increased the numbers of α-SMA-positive myofibroblasts, which were more prominent among AM+/- cells. TGF-ß-stimulated AM+/- myofibroblasts were larger and exhibited greater contractility and extracellular matrix production than WT cells. These cells were α-SMA (+), F-actin (+), and Ki-67(-) and appeared to be nonproliferating myofibroblasts (non-p-MyoFbs), which contribute to the severity of fibrosis. Our findings suggest that in addition to suppressing inflammation, the AM-RAMP2 system ameliorates pulmonary fibrosis by suppressing TGF-ß-Smad3 signaling, microRNA-21 activity and differentiation into non-p-MyoFbs.

Adrenomedullin-RAMP2 and -RAMP3 Systems Regulate Cardiac Homeostasis during Cardiovascular Stress.

Adrenomedullin (AM) is a peptide hormone with multiple physiological functions, which are regulated by its receptor activity-modifying proteins, RAMP2 and RAMP3. We previously reported that AM or RAMP2 knockout (KO) (AM-/-, RAMP2-/-) is embryonically lethal in mice, whereas RAMP3-/- mice are apparently normal. AM, RAMP2, and RAMP3 are all highly expressed in the heart; however, their functions there are not fully understood. Here, we analyzed the pathophysiological functions of the AM-RAMP2 and AM-RAMP3 systems in hearts subjected to cardiovascular stress. Cardiomyocyte-specific RAMP2-/- (C-RAMP2-/-) and RAMP3-/- showed no apparent heart failure at base line. After 1 week of transverse aortic constriction (TAC), however, C-RAMP2-/- exhibited significant cardiac hypertrophy, decreased ejection fraction, and increased fibrosis compared with wild-type mice. Both dP/dtmax and dP/dtmin were significantly reduced in C-RAMP2-/-, indicating reduced ventricular contractility and relaxation. Exposing C-RAMP2-/- cardiomyocytes to isoproterenol enhanced their hypertrophy and oxidative stress compared with wild-type cells. C-RAMP2-/- cardiomyocytes also contained fewer viable mitochondria and showed reduced mitochondrial membrane potential and respiratory capacity. RAMP3-/- also showed reduced systolic function and enhanced fibrosis after TAC, but those only became apparent after 4 weeks. A reduction in cardiac lymphatic vessels was the characteristic feature in RAMP3-/-. These observations indicate the AM-RAMP2 system is necessary for early adaptation to cardiovascular stress through regulation of cardiac mitochondria. AM-RAMP3 is necessary for later adaptation through regulation of lymphatic vessels. The AM-RAMP2 and AM-RAMP3 systems thus play separate critical roles in the maintenance of cardiovascular homeostasis against cardiovascular stress.

Adrenomedullin-Receptor Activity-Modifying Protein 2 System Ameliorates Subretinal Fibrosis by Suppressing Epithelial-Mesenchymal Transition in Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is a leading cause of visual impairment. Anti-vascular endothelial growth factor drugs used to treat AMD carry the risk of inducing subretinal fibrosis. We investigated the use of adrenomedullin (AM), a vasoactive peptide, and its receptor activity-modifying protein 2, RAMP2, which regulate vascular homeostasis and suppress fibrosis. The therapeutic potential of the AM-RAMP2 system was evaluated after laser-induced choroidal neovascularization (LI-CNV), a mouse model of AMD. Neovascular formation, subretinal fibrosis, and macrophage invasion were all enhanced in both AM and RAMP2 knockout mice compared with those in wild-type mice. These pathologic changes were suppressed by intravitreal injection of AM. Comprehensive gene expression analysis of the choroid after LI-CNV with or without AM administration revealed that fibrosis-related molecules, including Tgfb, Cxcr4, Ccn2, and Thbs1, were all down-regulated by AM. In retinal pigment epithelial cells, co-administration of transforming growth factor-ß and tumor necrosis factor-α induced epithelial-mesenchymal transition, which was also prevented by AM. Finally, transforming growth factor-ß and C-X-C chemokine receptor type 4 (CXCR4) inhibitors eliminated the difference in subretinal fibrosis between RAMP2 knockout and wild-type mice. These findings suggest the AM-RAMP2 system suppresses subretinal fibrosis in LI-CNV by suppressing epithelial-mesenchymal transition.

Production of genetically engineered mice with higher efficiency, lower mosaicism, and multiplexing capability using maternally expressed Cas9.

The CRISPR/Cas9 system is widely used to generate gene-edited animals. Here, we developed an efficient system for generating genetically modified mice using maternal Cas9 from Cas9 transgenic mice. Using this system, we achieved lower mosaicism and higher rates of knock-in success, gene-editing, and birth compared to the similar parameters obtained using exogenously administered Cas9 (mRNA/protein) system. Furthermore, we successfully induced simultaneous mutations at multiple loci (a maximum of nine). Our novel gene-editing system based on maternal Cas9 could potentially facilitate the generation of mice with single and multiple gene modifications.

Deficiency of the adrenomedullin-RAMP3 system suppresses metastasis through the modification of cancer-associated fibroblasts.

Tumor metastasis is a primary source of morbidity and mortality in cancer. Adrenomedullin (AM) is a multifunctional peptide regulated by receptor activity-modifying proteins (RAMPs). We previously reported that the AM-RAMP2 system is involved in tumor angiogenesis, but the function of the AM-RAMP3 system remains largely unknown. Here, we investigated the actions of the AM-RAMP2 and 3 systems in the tumor microenvironment and their impact on metastasis. PAN02 pancreatic cancer cells were injected into the spleens of mice, leading to spontaneous liver metastasis. Tumor metastasis was enhanced in vascular endothelial cell-specific RAMP2 knockout mice (DI-E-RAMP2-/-). By contrast, metastasis was suppressed in RAMP3-/- mice, where the number of podoplanin (PDPN)-positive cancer-associated fibroblasts (CAFs) was reduced in the periphery of tumors at metastatic sites. Because PDPN-positive CAFs are a hallmark of tumor malignancy, we assessed the regulation of PDPN and found that Src/Cas/PDPN signaling is mediated by RAMP3. In fact, RAMP3 deficiency CAFs suppressed migration, proliferation, and metastasis in co-cultures with tumor cells in vitro and in vivo. Moreover, the activation of RAMP2 in RAMP3-/- mice suppressed both tumor growth and metastasis. Based on these results, we suggest that the upregulation of PDPN in DI-E-RAMP2-/- mice increases malignancy, while the downregulation of PDPN in RAMP3-/- mice reduces it. Selective activation of RAMP2 and inhibition of RAMP3 would therefore be expected to suppress tumor metastasis. This study provides the first evidence that understanding and targeting to AM-RAMP systems could contribute to the development of novel therapeutics against metastasis.

Endogenous Calcitonin Gene-Related Peptide Deficiency Exacerbates Postoperative Lymphedema by Suppressing Lymphatic Capillary Formation and M2 Macrophage Accumulation.

Lymphedema is a chronic condition caused by disruption of lymphatic vessels, which often occurs after invasive surgery. Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide produced by alternative splicing of the primary transcript of the calcitonin/CGRP gene (Calca). CGRP was initially identified as a neuropeptide released primarily from sensory nerves and involved in regulating pathophysiological nociceptive pain. However, recent studies have shown CGRP is also released from a variety of other cells and possesses multiple functions. In this study, CGRP knockout (-/-) mice were used to show the actions of endogenous CGRP in postoperative lymphedema. After generating a mouse postoperative tail lymphedema model, the edema was observed to be more severe in CGRP-/- mice than in wild-type mice. Numbers of lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1)-positive lymphatic capillaries were decreased and lymphatic capillary formation-related factors were down-regulated in CGRP-/- mice. In addition, accumulation of M2 but not M1 macrophages was selectively reduced in the edematous tissue of CGRP-/- mice. Selective depletion of M2 macrophages decreased lymphatic capillary formation and worsened lymphedema in wild-type mice but not CGRP-/- mice, where numbers of M2 macrophages were already diminished. These findings suggest that endogenous CGRP acts to ameliorate postoperative lymphedema by enhancing lymphatic capillary formation and that M2 macrophages play critical roles. CGRP may be a useful therapeutic target for the treatment of postoperative lymphedema.

Development of a Novel Model of Central Retinal Vascular Occlusion and the Therapeutic Potential of the Adrenomedullin-Receptor Activity-Modifying Protein 2 System.

Central retinal vein occlusion (CRVO) is an intractable disease that causes visual acuity loss with retinal ischemia, hemorrhage, and edema. In this study, we developed an experimental CRVO model in mice and evaluated the therapeutic potential of the pleiotropic peptide adrenomedullin (ADM) and its receptor activity-modifying protein 2 (RAMP2). The CRVO model, which had phenotypes resembling those seen in the clinic, was produced by combining i.p. injection of Rose bengal, a photoactivator dye enhancing thrombus formation, with laser photocoagulation. Retinal vascular area, analyzed using fluorescein angiography and fluorescein isothiocyanate-perfused retinal flat mounts, was decreased after induction of CRVO but gradually recovered from day 1 to 7. Measurements of retinal thickness using optical coherence tomography and histology revealed prominent edema early after CRVO, followed by gradual atrophy. Reperfusion after CRVO was diminished in Adm and Ramp2 knockout (KO) mice but was increased by exogenous ADM administration. CRVO also increased expression of a coagulation factor, oxidative stress markers, and a leukocyte adhesion molecule in both wild-type and Adm KO mice, and the effect was more pronounced in Adm KO mice. Using retinal capillary endothelial cells, ADM was found to directly suppress retinal endothelial injury. The retinoprotective effects of the Adm-Ramp2 system make it a novel therapeutic target for the treatment of CRVO.

Regulation of cardiovascular development and homeostasis by the adrenomedullin-RAMP system.

Adrenomedullin (AM), a member of the calcitonin peptide superfamily, is a peptide involved in both the pathogenesis of cardiovascular diseases and circulatory homeostasis. Its receptor, calcitonin receptor-like receptor (CLR), associates with an accessory protein, receptor activity-modifying protein (RAMP). Depending upon which the three RAMP isoforms (RAMP1-3) it interacts with, CLR functions as a receptor for AM or other calcitonin family peptides. AM knockout mice (-/-) died mid-gestation due to abnormalities in vascular development. We found that phenotypes similar to AM-/- were reproduced only in RAMP2-/- mice. We generated endothelial cell-specific RAMP2 knockout mice (E-RAMP2-/-) and found most E-RAMP2-/- mice died perinatally. In surviving adults, vasculitis and organ fibrosis occurred spontaneously. We next generated drug-inducible cardiac myocyte-specific RAMP2-/- (DI-C-RAMP2-/-) mice, which exhibited dilated cardiomyopathy-like heart failure with cardiac dilatation and myofibril disruption. DI-C-RAMP2-/- hearts also showed changes in mitochondrial structure and downregulation of mitochondria-related genes involved in oxidative phosphorylation and ß-oxidation. In contrast to RAMP2-/- mice, RAMP3-/- mice were born with no major abnormalities. In adult RAMP3-/- mice, postnatal angiogenesis was normal, but drainage of subcutaneous lymphatic vessels was delayed. RAMP3-/- mice also showed more severe interstitial edema than in wild-type mice in a tail lymphedema model. These findings show that the AM-RAMP system is a key determinant of cardiovascular integrity and homeostasis from prenatal stages through adulthood. The AM-RAMP2 system mainly regulates vascular development and homeostasis, while the AM-RAMP3 system mainly regulates lymphatic function in adults. The AM-RAMP system may thus have therapeutic potential for the treatment of cardiovascular diseases.

RAMP3 deficiency enhances postmenopausal obesity and metabolic disorders.

There is a marked increase in the incidence of visceral adiposity and insulin resistance among women following menopause. Adrenomedullin (AM) is an endogenous peptide first identified as a vasodilator, but now known to exert a variety of physiological effects. RAMP3 is a receptor activity-modifying protein that binds to the AM receptor (calcitonin receptor-like receptor). As expression of both AM and RAMP3 is reportedly activated by estrogen, we hypothesized that RAMP3 is crucially involved in the pathophysiology of postmenopausal obesity. To test this idea, we compared the effects of ovariectomy (OVX) and a high-fat diet for 10 weeks (a model of postmenopausal obesity) between RAMP3 knockout (RAMP3-/-) and wild-type mice. RAMP3-/- OVX mice exhibited greater obesity and adipose tissue weight gain as compared to wild-type OVX mice. RAMP3-/- OVX mice also exhibited higher serum insulin levels. In periuterine WAT from RAMP3-/- OVX mice, expression of lipolysis-related factors was lower and expression of inflammation-related factors was higher than in wild-type OVX mice. Hepatic steatosis was also exacerbated in RAMP3-/- OVX. Notably, expression of the membrane-type estrogen receptor GPR30 was downregulated in periuterine WAT from RAMP3-/- OVX mice. These findings raise the possibility that a GPR30-RAMP3 interaction is involved in the pathophysiology of postmenopausal obesity and suggest RAMP3 plays a key role in the regulation of energy metabolism and exerts a hepatoprotective effect in this model of postmenopausal obesity. RAMP3 may thus be a useful therapeutic target for treatment of postmenopausal obesity and metabolic disorders.

Endogenous calcitonin gene-related peptide suppresses ischemic brain injuries and progression of cognitive decline.

BACKGROUND: Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide and produced by alternative splicing of the transcript of the calcitonin/CGRP gene. Originally identified as a strong vasodilatory and hypotensive peptide, CGRP is now known to be a pleiotropic molecule distributed in various organs, including the brain. METHOD: In this study, we used CGRP knockout mice (CGRP-/-) to examine the actions of endogenous CGRP during cerebral ischemia. To induce acute and chronic cerebral ischemia, mice were subjected to middle cerebral artery occlusion (MCAO) and bilateral common carotid artery stenosis (BCAS). RESULTS: In the cerebral cortex of wild-type mice, CGRP expression was upregulated after acute infarction. In CGRP-/- subjected to MCAO or BCAS, recovery of cerebral blood flow was slower and exhibited more extensive neuronal cell death. Expression of the inflammatory cytokines was higher in CGRP-/- than wild type in the acute phase of ischemia. Pathological analysis during the chronic phase revealed more extensive neuronal cell loss and demyelination and higher levels of oxidative stress in CGRP-/- than wild-type. CGRP-/- also showed less compensatory capillary growth. In an eight-arm radial maze test, CGRP-/- exhibited poorer reference memory than wild-type. On the other hand, CGRP administration promoted cerebral blood flow recovery after cerebral ischemia. We also found that CGRP directly inhibited the cell death of primary cortical neurons. CONCLUSION: These results indicate endogenous CGRP is protective against ischemia-induced neuronal cell injury. CGRP could, thus, be a novel candidate for use in the treatment of both cerebral ischemia and progression of cognitive decline.

Adrenomedullin Suppresses Vascular Endothelial Growth Factor-Induced Vascular Hyperpermeability and Inflammation in Retinopathy.

Diabetic macular edema (DME) is caused by blood-retinal barrier breakdown associated with retinal vascular hyperpermeability and inflammation, and it is the major cause of visual dysfunction in diabetic retinopathy. Adrenomedullin (ADM) is an endogenous peptide first identified as a strong vasodilator. ADM is expressed in the eyes and is up-regulated in various eye diseases, although the pathophysiological significance is largely unknown. We investigated the effect of ADM on DME. In Kimba mice, which overexpress human vascular endothelial growth factor in their retinas, the capillary dropout, vascular leakage, and vascular fragility characteristic of diabetic retinopathy were observed. Intravitreal or systemic administration of ADM to Kimba mice ameliorated both the capillary dropout and vascular leakage. Evaluation of the transendothelial electrical resistance and fluorescein isothiocyanate-dextran permeability of an endothelial cell monolayer using TR-iBRB retinal capillary endothelial cells revealed that vascular endothelial growth factor enhanced vascular permeability but that co-administration of ADM suppressed the effect, in part by enhancing tight junction formation between endothelial cells. In addition, a comprehensive PCR array analysis showed that ADM administration suppressed various molecules related to inflammation and NF-κB signaling within retinas. From these results, we suggest that by exerting inhibitory effects on retinal inflammation, vascular permeability, and blood-retinal barrier breakdown, ADM could serve as a novel therapeutic agent for the treatment of DME.

Endogenous Calcitonin Gene-Related Peptide Regulates Lipid Metabolism and Energy Homeostasis in Male Mice.

Calcitonin gene-related peptide (CGRP) is a bioactive peptide produced by alternative splicing of the primary transcript of the calcitonin/CGRP gene. CGRP is largely distributed in the cardiovascular and nervous systems, where it acts as a regulatory factor. CGRP is also expressed in organs and tissues involved in metabolic regulation, including white adipose tissue (WAT), where its function is largely unknown. In this study, we examined the effects of endogenous CGRP on metabolic function. When we administered a high-fat diet to CGRP-specific knockout (CGRP-/-) and wild-type (WT) mice for 10 weeks, we observed that food intake did not differ between the two groups, but body weight and visceral fat weight were significantly lower in CGRP-/- mice. Fatty liver changes were less severe in CGRP-/- mice, which also showed lower serum insulin and leptin levels. Glucose tolerance and insulin sensitivity were better in CGRP-/- than WT mice, and expired gas analysis revealed greater oxygen consumption by CGRP-/- mice. Adipocyte hypertrophy was suppressed in CGRP-/- mice, while expression of ß-3-adrenergic receptor, hormone-sensitive lipase and adiponectin was enhanced. Isoproterenol-induced glycerol release from WAT was higher in CGRP-/- than WT mice, and CGRP-/- mice showed elevated sympathetic nervous activity. ß-receptor-blockade canceled the beneficial effects of CGRP deletion on obesity. These results suggest that, in addition to its actions in the cardiovascular system, endogenous CGRP is a key regulator of metabolism and energy homeostasis in vivo.

Vasoprotective Activities of the Adrenomedullin-RAMP2 System in Endothelial Cells.

Neointimal hyperplasia is the primary lesion underlying atherosclerosis and restenosis after coronary intervention. We previously described the essential angiogenic function of the adrenomedullin (AM)-receptor activity-modifying protein (RAMP) 2 system. In the present study, we assessed the vasoprotective actions of the endogenous AM-RAMP2 system using a wire-induced vascular injury model. We found that neointima formation and vascular smooth muscle cell proliferation were enhanced in RAMP2+/- male mice. The injured vessels from RAMP2+/- mice showed greater macrophage infiltration, inflammatory cytokine expression, and oxidative stress than vessels from wild-type mice and less re-endothelialization. After endothelial cell-specific RAMP2 deletion in drug-inducible endothelial cell-specific RAMP2-/- (DI-E-RAMP2-/-) male mice, we observed markedly greater neointima formation than in control mice. In addition, neointima formation after vessel injury was enhanced in mice receiving bone marrow transplants from RAMP2+/- or DI-E-RAMP2-/- mice, indicating that bone marrow-derived cells contributed to the enhanced neointima formation. Finally, we found that the AM-RAMP2 system augmented proliferation and migration of endothelial progenitor cells. These results demonstrate that the AM-RAMP2 system exerts crucial vasoprotective effects after vascular injury and could be a therapeutic target for the treatment of vascular diseases.

The endothelial adrenomedullin-RAMP2 system regulates vascular integrity and suppresses tumour metastasis.

AIMS: Controlling vascular integrity is expected to be a novel therapeutic target of cancers as well as cardiovascular diseases. Adrenomedullin (AM) and its receptor-modulating protein, RAMP2, have been identified as essential mediators of cardiovascular homeostasis. In this study, we used inducible vascular endothelial cell-specific RAMP2 knockout (DI-E-RAMP2(-/-)) mice to clarify the contribution made by the endogenous AM-RAMP2 system to angiogenesis and metastasis. METHODS AND RESULTS: Subcutaneously transplanted sarcoma or melanoma cells showed less growth and angiogenesis in DI-E-RAMP2(-/-) than in control mice. On the other hand, after the transplantation of B16BL6 melanoma cells into hindlimb footpads, spontaneous metastasis to the lung was enhanced in DI-E-RAMP2(-/-) mice. Early after RAMP2 gene deletion, DI-E-RAMP2(-/-) mice showed enhanced vascular permeability, endothelial-mesenchymal transition (EndMT)-like change, and systemic oedema. Within the lungs of DI-E-RAMP2(-/-) mice, pulmonary endothelial cells were deformed, and inflammatory cells infiltrated the vessel walls and expressed the chemotactic factors S100A8/9 and SAA3, which attract tumour cells and mediate the formation of a pre-metastatic niche. Conversely, the overexpression of RAMP2 suppressed tumour cell adhesion to endothelial cells, tumour metastasis, and improved survival. CONCLUSION: These findings indicate that the AM-RAMP2 system regulates vascular integrity, whereas RAMP2 deletion promotes vascular permeability and EndMT-like change within primary lesions and formation of pre-metastatic niches in distant organs by destabilizing the vascular structure and inducing inflammation. Vascular integrity regulated by the AM-RAMP2 system could thus be a hopeful therapeutic target for suppressing tumour metastasis.

A non-inheritable maternal Cas9-based multiple-gene editing system in mice.

The CRISPR/Cas9 system is capable of editing multiple genes through one-step zygote injection. The preexisting method is largely based on the co-injection of Cas9 DNA (or mRNA) and guide RNAs (gRNAs); however, it is unclear how many genes can be simultaneously edited by this method, and a reliable means to generate transgenic (Tg) animals with multiple gene editing has yet to be developed. Here, we employed non-inheritable maternal Cas9 (maCas9) protein derived from Tg mice with systemic Cas9 overexpression (Cas9 mice). The maCas9 protein in zygotes derived from mating or in vitro fertilization of Tg/+ oocytes and +/+ sperm could successfully edit the target genome. The efficiency of such maCas9-based genome editing was comparable to that of zygote microinjection-based genome editing widely used at present. Furthermore, we demonstrated a novel approach to create "Cas9 transgene-free" gene-modified mice using non-Tg (+/+) zygotes carrying maCas9. The maCas9 protein in mouse zygotes edited nine target loci simultaneously after injection with nine different gRNAs alone. Cas9 mouse-derived zygotes have the potential to facilitate the creation of genetically modified animals carrying the Cas9 transgene, enabling repeatable genome engineering and the production of Cas9 transgene-free mice.

Adrenomedullin-RAMP2 System in Vascular Endothelial Cells.

Vascular endothelial cells play key roles in maintaining vascular and organ homeostasis. Adrenomedullin (AM), originally identified as a vasodilating peptide, is now recognized to be a pleiotropic molecule involved in both circulatory homeostasis and the pathogenesis of cardiovascular diseases. We have reported that knockout mice deficient in AM or receptor activity-modifying protein 2 (RAMP2), an AM-receptor accessory protein, show vascular endothelial cell deformities that are embryonically lethal. To directly clarify the pathophysiological functions of the vascular AM-RAMP2 system, we generated vascular endothelial cell-specific RAMP2 knockout mice. Using these mice, we found that the AM-RAMP2 system is a key determinant of vascular integrity and homeostasis from prenatal stages through adulthood. This review highlights the functions of AM-RAMP2 in vascular endothelial cells.

Pathophysiological function of endogenous calcitonin gene-related peptide in ocular vascular diseases.

Calcitonin gene-related peptide (CGRP; official name CALCA) has a variety of functions and exhibits both angiogenic and anti-inflammatory properties. We previously reported the angiogenic effects of the CGRP family peptide adrenomedullin in oxygen-induced retinopathy; however, the effects of CGRP on ocular angiogenesis remain unknown. Herein, we used CGRP knockout (CGRP(-/-)) mice to investigate the roles of CGRP in ocular vascular disease. Observation of pathological retinal angiogenesis in the oxygen-induced retinopathy model revealed no difference between CGRP(-/-) and wild-type mice. However, much higher levels of the CGRP receptor were present in the choroid than the retina. Laser-induced choroidal neovascularization (CNV), a model of exudative age-related macular degeneration, revealed more severe CNV lesions in CGRP(-/-) than wild-type mice, and fluorescein angiography showed greater leakage from CNV in CGRP(-/-). In addition, macrophage infiltration and tumor necrosis factor (TNF)-α production were enhanced within the CNV lesions in CGRP(-/-) mice, and the TNF-α, in turn, suppressed the barrier formation of retinal pigment epithelial cells. In vivo, CGRP administration suppressed CNV formation, and CGRP also dose dependently suppressed TNF-α production by isolated macrophages. From these data, we conclude that CGRP suppresses the development of leaky CNV through negative regulation of inflammation. CGRP may thus be a promising therapeutic agent for the treatment of ocular vascular diseases associated with inflammation.