Cancer protection elicited by a single nucleotide polymorphism close to the adrenomedullin gene

Adrenomedullin as a potential biomarker involved in patients with hereditary hemorrhagic telangiectasia

BACKGROUND

Adrenomedullin (AM) is a vasoactive peptide mostly secreted by endothelial cells with an important role in preserving endothelial integrity.  The relationship between AM and hereditary hemorrhagic telangiectasia (HHT) is unknown. We aimed to compare the serum levels and tissue expression of AM between HHT patients and controls.

METHODS

Serum AM levels were measured by radioimmunoassay and compared between control and HHT groups. AM levels were also compared among HHT subgroups according to clinical characteristics. The single nucleotide polymorphism (SNP) rs4910118 was assessed by restriction analysis and sequencing. AM immunohistochemistry was performed on biopsies of cutaneous telangiectasia from eight HHT patients and on the healthy skin from five patients in the control group.

RESULTS

Forty-five HHT patients and 50 healthy controls were included, mean age (SD) was 50.7 (14.9) years and 46.4 (9.9) years (p = 0.102), respectively. HHT patients were mostly female (60% vs 38%, p = 0.032). Median [Q1-Q3] serum AM levels were 68.3 [58.1-80.6] pg/mL in the HHT group and 47.7 [43.2-53.8] pg/mL in controls (p<0.001), with an optimal AM cut-off according to Youden's J statistic of 55.32 pg/mL (J:0.729). Serum AM levels were similar in the HHT subgroups. No patient with HHT had the SNP rs4910118. AM immunoreactivity was found with high intensity in the abnormal blood vessels of HHT biopsies.

CONCLUSIONS

We detected higher AM serum levels and tissue expression in patients with HHT than in healthy controls. The role of AM in HHT, and whether AM may constitute a novel biomarker and therapeutic target, needs further investigation.

Protein disulphide isomerase can predict the clinical prognostic value and contribute to malignant progression in gliomas

Increasing evidence from structural and functional studies has indicated that protein disulphide isomerase (PDI) has a critical role in the proliferation, survival and metastasis of several types of cancer. However, the molecular mechanisms through which PDI contributes to glioma remain unclear. Here, we aimed to investigate whether the differential expression of 17 PDI family members was closely related to the different clinicopathological features in gliomas from The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas data sets. Additionally, four subgroups of gliomas (cluster 1/2/3/4) were identified based on consensus clustering of the PDI gene family. These findings not only demonstrated that a poorer prognosis, higher WHO grade, lower frequency of isocitrate dehydrogenase mutation and higher 1p/19q non‐codeletion status were significantly correlated with cluster 4 compared with the other clusters, but also indicated that the malignant progression of glioma was closely correlated with the expression of PDI family members. Moreover, we also constructed an independent prognostic marker that can predict the clinicopathological features of gliomas. Overall, the results indicated that PDI family members may serve as possible diagnostic markers in gliomas.

Lack of Adrenomedullin Aggravates Acute TNBS-Induced Colitis Symptoms in Mice, Especially in Females

Adrenomedullin (AM) is a biologically active peptide which has been tested as a new therapy for inflammatory bowel disease (IBD) in animal models and in patients with severe ulcerative colitis. We used an inducible knockout (KO) mouse model for AM to evaluate the effects of endogenous levels of this peptide on the development and degree of pathogenesis of IBD. Acute colitis was induced in mice of both sexes by rectal instillation of 3 mg 2,4,6-trinitrobenzenesulfonic acid (TNBS) in 100 μL of 50% ethanol. Control mice received the same volume of saline in 50% ethanol. During the following 5 days, the weight and the disease severity index of all animals were recorded. After sacrifice, the inflammatory response was macroscopically assessed by analyzing the weight of the colon; by histomorphometrical analysis on histological sections; and by qRT-PCR determination of different inflammatory, adhesion, and regeneration molecules. TNBS administration caused a significantly more severe colitis in KO mice, and especially in females, when compared to wild type (WT) animals. Abrogation of the AM gene caused more severe diarrhea, accompanied by rectal bleeding, anorexia, and a significant increase of colon weight. Histological analysis of TNBS-treated KO mice showed large areas of lymphocyte infiltrates in the mucosa and submucosa, with loss of tissue architecture. No alterations were observed in the expression levels of inflammatory cytokines at the time of sacrifice; meanwhile lack of AM resulted in lower levels of some adhesion molecules and regeneration markers. Taken together, these results support the protective role of endogenous AM against the development of acute colitis, and that its effects are particularly beneficial on females.

Adrenomedullin Contributes to Age-Related Memory Loss in Mice and Is Elevated in Aging Human Brains

Memory decline is common in elderly individuals and is the hallmark of Alzheimer’s disease (AD). Memory failure follows the loss of synaptic contacts in the cerebral cortex and hippocampus, caused in part by cytoskeleton disruption. Adrenomedullin (AM) and its gene-related peptide, proadrenomedullin N-terminal 20 peptide (PAMP), are microtubule-associated proteins (MAP) whose expression has been identified as a potential biomarker for predicting progression from predementia to clinical AD. Here we analyze the connection between AM levels and memory preservation. Mice lacking neuronal AM and PAMP (knockout, KO) and their wild type (WT) littermates were subjected, at different ages, to the novel object recognition test and the contextual fear conditioned test. Aged KO mice have significantly better retention memory than their WT counterparts. This feature was more prominent in females than in males. Prefrontal cortex and hippocampus samples from these animals were subjected to Western blotting for phospho-Tau and acetylated tubulin. Aged female KO mice had significantly less accumulation of phospho-Tau than their WT littermates. In addition, protein extracts from the frontal cortex of non-demented mature (65.10 ± 3.86 years) and aged (77.14 ± 2.77 years) human donors were analyzed by Western blotting. Aged human brains had significantly higher levels of AM and lower levels of acetylated tubulin than younger donors. These observations suggest that drugs or interventions that reduce AM/PAMP expression may constitute a new avenue to prevent memory decline during normal aging and in patients suffering moderate AD in high risk of rapid cognitive decline.

Lack of Adrenomedullin Results in Microbiota Changes and Aggravates Azoxymethane and Dextran Sulfate Sodium-Induced Colitis in Mice

The link between intestinal inflammation, microbiota, and colorectal cancer is intriguing and the potential underlying mechanisms remain unknown. Here we evaluate the influence of adrenomedullin (AM) in microbiota composition and its impact on colitis with an inducible knockout (KO) mouse model for AM. Microbiota composition was analyzed in KO and wild type (WT) mice by massive sequencing. Colitis was induced in mice by administration of azoxymethane (AOM) followed by dextran sulfate sodium (DSS) in the drinking water. Colitis was evaluated using a clinical symptoms index, histopathological analyses, and qRT-PCR. Abrogation of the adm gene in the whole body was confirmed by PCR and qRT-PCR. KO mice exhibit significant changes in colonic microbiota: higher proportion of δ-Proteobacteria class; of Coriobacteriales order; and of other families and genera was observed in KO feces. Meanwhile these mice had a lower proportion of beneficial bacteria, such as Lactobacillus gasseri and Bifidobacterium choerinum. TLR4 gene expression was higher (p < 0.05) in KO animals. AM deficient mice treated with DSS exhibited a significantly worse colitis with profound weight loss, severe diarrhea, rectal bleeding, colonic inflammation, edema, infiltration, crypt destruction, and higher levels of pro-inflammatory cytokines. No changes were observed in the expression levels of adhesion molecules. In conclusion, we have shown that lack of AM leads to changes in gut microbiota population and in a worsening of colitis conditions, suggesting that endogenous AM is a protective mediator in this pathology.

Lack of adrenomedullin in mouse endothelial cells results in defective angiogenesis, enhanced vascular permeability, less metastasis, and more brain damage

Adrenomedullin (AM) is a vasodilating peptide involved in the regulation of circulatory homeostasis and in the pathophysiology of certain cardiovascular diseases. AM plays critical roles in blood vessels, including regulation of vascular stability and permeability. To elucidate the autocrine/paracrine function of AM in endothelial cells (EC) in vivo, a conditional knockout of AM in EC (AM(EC-KO)) was used. The amount of vascularization of the matrigel implants was lower in AM(EC-KO) mice indicating a defective angiogenesis. Moreover, ablation of AM in EC revealed increased vascular permeability in comparison with wild type (WT) littermates. In addition, AM(EC-KO) lungs exhibited significantly less tumor growth than littermate WT mice using a syngeneic model of metastasis. Furthermore, following middle cerebral artery permanent occlusion, there was a significant infarct size decrease in animals lacking endothelial AM when compared to their WT counterparts. AM is an important regulator of EC function, angiogenesis, tumorigenesis, and brain response to ischemia. Studies of AM should bring novel approaches to the treatment of vascular diseases.

Adrenomedullin regulates intestinal physiology and pathophysiology

Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are 2 biologically active peptides produced by the same gene, ADM, with ubiquitous distribution and many physiological functions. Adrenomedullin is composed of 52 amino acids, has an internal molecular ring composed by 6 amino acids and a disulfide bond, and shares structural similarities with calcitonin gene-related peptide, amylin, and intermedin. The AM receptor consists of a 7-transmembrane domain protein called calcitonin receptor-like receptor in combination with a single transmembrane domain protein known as receptor activity-modifying protein. Using morphologic techniques, it has been shown that AM and PAMP are expressed throughout the gastrointestinal tract, being specially abundant in the neuroendocrine cells of the gastrointestinal mucosa; in the enterochromaffin-like and chief cells of the gastric fundus; and in the submucosa of the duodenum, ileum, and colon. This wide distribution in the gastrointestinal tract suggests that AM and PAMP may act as gut hormones regulating many physiological and pathologic conditions. To date, it has been proven that AM and PAMP act as autocrine/paracrine growth factors in the gastrointestinal epithelium, play key roles in the protection of gastric mucosa from various kinds of injury, and accelerate healing in diseases such as gastric ulcer and inflammatory bowel diseases. In addition, both peptides are potent inhibitors of gastric acid secretion and gastric emptying; they regulate the active transport of sugars in the intestine, regulate water and ion transport in the colon, modulate colonic bowel movements and small-intestine motility, improve endothelial barrier function, and stabilize circulatory function during gastrointestinal inflammation. Furthermore, AM and PAMP are antimicrobial peptides, and they contribute to the mucosal host defense system by regulating gut microbiota. To get a formal demonstration of the effects that endogenous AM and PAMP may have in gut microbiota, we developed an inducible knockout of the ADM gene. Using this model, we have shown, for the first time, that lack of AM/PAMP leads to changes in gut microbiota composition in mice. Further studies are needed to investigate whether this lack of AM/PAMP may have an impact in the development and/or progression of intestinal diseases through their effect on microbiota composition.

Prevention of Bone Loss in a Model of Postmenopausal Osteoporosis through Adrenomedullin Inhibition

Despite recent advances in the understanding and treatment options for osteoporosis, this condition remains a serious public health issue. Adrenomedullin (AM) is a regulatory peptide with reported activity on bone remodeling. To better understand this relationship we built an inducible knockout for AM. An outstanding feature of knockout mice is their heavier weight due, in part, to the presence of denser bones. The femur of knockout animals was denser, had more trabeculae, and a thicker growth plate than wild type littermates. The endocrine influence of AM on bone seems to be elicited through an indirect mechanism involving, at least, the regulation of insulin, glucose, ghrelin, and calcitonin gene-related peptide (CGRP). To confirm the data we performed a pharmacological approach using the AM inhibitor 16311 in a mouse model of osteoporosis. Ovariectomized females showed significant bone mass loss, whereas ovariectomized females treated with 16311 had similar bone density to sham operated females. In conclusion, we propose the use of AM inhibitors for the treatment of osteoporosis and other conditions leading to the loss of bone mass.

Adrenomedullin and tumour microenvironment

Adrenomedullin (AM) is a regulatory peptide whose involvement in tumour progression is becoming more relevant with recent studies. AM is produced and secreted by the tumour cells but also by numerous stromal cells including macrophages, mast cells, endothelial cells, and vascular smooth muscle cells. Most cancer patients present high levels of circulating AM and in some cases these higher levels correlate with a worst prognosis. In some cases it has been shown that the high AM levels return to normal following surgical removal of the tumour, thus indicating the tumour as the source of this excessive production of AM. Expression of this peptide is a good investment for the tumour cell since AM acts as an autocrine/paracrine growth factor, prevents apoptosis-mediated cell death, increases tumour cell motility and metastasis, induces angiogenesis, and blocks immunosurveillance by inhibiting the immune system. In addition, AM expression gets rapidly activated by hypoxia through a HIF-1α mediated mechanism, thus characterizing AM as a major survival factor for tumour cells. Accordingly, a number of studies have shown that inhibition of this peptide or its receptors results in a significant reduction in tumour progression. In conclusion, AM is a great target for drug development and new drugs interfering with this system are being developed.

Adrenomedullin protects from experimental autoimmune encephalomyelitis at multiple levels

Adrenomedullin is a neuropeptide known for its cardiovascular activities and anti-inflammatory effects. Here, we investigated the effect of adrenomedullin in a model of experimental autoimmune encephalomyelitis (EAE) that mirrors chronic progressive multiple sclerosis. A short-term systemic treatment with adrenomedullin reduced clinical severity and incidence of EAE, the appearance of inflammatory infiltrates in spinal cord and the subsequent demyelination and axonal damage. This effect was exerted at multiple levels affecting both early and late events of the disease. Adrenomedullin decreased the presence/activation of encephalitogenic Th1 and Th17 cells and down-regulated several inflammatory mediators in peripheral lymphoid organs and central nervous system. Noteworthy, adrenomedullin inhibited the production by encephalitogenic cells of osteopontin and of Granulocyte Macrophage Colony-Stimulating Factor (GM-CSF), two critical cytokines in the development of EAE. At the same time, adrenomedullin increased the number of IL-10-producing regulatory T cells with suppressive effects on the progression of EAE. Furthermore, adrenomedullin generated dendritic cells with a semi-mature phenotype that impaired encephalitogenic responses in vitro and in vivo. Finally, adrenomedullin regulated glial activity and favored an active program of neuroprotection/regeneration. Therefore, the use of adrenomedullin emerges as a novel multimodal therapeutic approach to treat chronic progressive multiple sclerosis.