Glucocorticoids alter adrenomedullin receptor expression and secretion in endothelial-like cells and astrocytes

Adrenomedullin mediates pro-angiogenic and pro-inflammatory cytokines in asthma and COPD

PURPOSE

Adrenomedullin (AM) is a pluripotent peptide hormone with contradictory effects in human health and disease. In chronic inflammatory lung diseases, such as asthma and COPD, AM has been shown to inhibit inflammation and cell proliferation. In the present study, we aimed to investigate the effect of AM on pro-angiogenic and pro-inflammatory cytokines in asthma and COPD.

PATIENTS AND METHODS

Serum levels of pro-AM were measured in patients with asthma, COPD and matched controls. The effect of AM on intracellular signaling proteins and cytokine secretion was assessed in primary cultures of epithelial cells (EC) and airway smooth muscle cells (ASMC) established from endo-bronchial biopsies of patients with asthma, COPD and controls.

RESULTS

Serum pro-AM was higher in patients with asthma and COPD, compared to controls. AM stimulated cAMP in ASMC but not in EC. In EC, AM decreased Erk1/2 MAPK expression and activation but in ASMC, AM activated Erk1/2. This effect was similar in asthma, COPD and controls. AM stimulated the secretion of pro-angiogenic CXCL1 by EC of controls and CXCL5 by EC of asthma patients. AM did not affect the secretion of IL-6 or IL-8 by EC but stimulated the secretion of IL-6 by ASMC. In EC, AM inhibited the stimulatory effect of TGF-β and IL-4 on the secretion of IL-6 and IL-8 but had an additive stimulatory effect with TGF-β in ASMC.

CONCLUSIONS

These data suggest that AM mediates the secretion of pro-angiogenic and pro-inflammatory cytokines in a cell-type and/or a disease-specific way, explaining its association with clinical outcomes in COPD.

Adrenomedullin, a Novel Target for Neurodegenerative Diseases

Neurodegenerative diseases represent a heterogeneous group of disorders whose common characteristic is the progressive degeneration of neuronal structure and function. Although much knowledge has been accumulated on the pathophysiology of neurodegenerative diseases over the years, more efforts are needed to understand the processes that underlie these diseases and hence to propose new treatments. Adrenomedullin (AM) is a multifunctional peptide involved in vasodilation, hormone secretion, antimicrobial defense, cellular growth, and angiogenesis. In neurons, AM and related peptides are associated with some structural and functional cytoskeletal proteins that interfere with microtubule dynamics. Furthermore, AM may intervene in neuronal dysfunction through other mechanisms such as immune and inflammatory response, apoptosis, or calcium dyshomeostasis. Alterations in AM expression have been described in neurodegenerative processes such as Alzheimer's disease or vascular dementia. This review addresses the current state of knowledge on AM and its possible implication in neurodegenerative diseases.

Plasmid pLXSN-Mediated Adrenomedullin Gene Therapy for Cerebral Vasospasm Following Subarachnoid Hemorrhage in Rats

Background

The aim of this study was to investigate the protective effect of ADM gene mediated by plasmid pVAX1 on cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH).

Material/Methods

The recombinant plasmid pVAX-ADM was successfully established, and 40 SD rats were randomly divided into normal saline, pVAX1, pVAX1-ADM low-dose, pVAX1-ADM mid-dose, and pVAX1-ADM high-dose groups. The circumference and diameter of basilar artery, diameter of middle cerebral artery and internal carotid artery, and thickness of basilar artery wall were observed. The levels of circulating endothelial cells (CEC) and levels of regional cerebral blood flow (rCBF) of the parietal cortex were detected at different time-points. The expression levels of serum ADM, ET-1, and NOS of each group and the neurological functions were compared.

Results

The circumference and diameter of basilar artery and the diameter of the middle cerebral artery and internal carotid artery in pVAX1-ADM groups were significantly longer than those in the saline group and pVAX1 group (P<0.05), but the thickness of the basilar artery wall in pVAX1-ADM groups was significantly lower (P<0.05), and the levels of growth or decrease were both dose-dependent (P<0.05). Compared with the saline group and pVAX1 group, the expression levels of serum ADM, NOS, and rCBF in pVAX1-ADM groups were significantly higher (P<0.05), but the levels of serum ET-1 and CEC were significantly lower (P<0.05). The scores of neurobehavioral functions of pVAX1-ADM groups were significantly lower (P<0.05), and the scores were also dose-dependent (P<0.05).

Conclusions

The recombinant eukaryotic expression plasmid pVAX1-ADM can significantly relieve cerebral vasospasm, increase the expression of serum ADM and NOS, and decrease the expression of serum ET-1 in a rat model of CVS; it is dose-dependent and can also improve nervous system function.

Inflammation Modulates RLIP76/RALBP1 Electrophile-Glutathione Conjugate Transporter and Housekeeping Genes in Human Blood-Brain Barrier Endothelial Cells

Endothelial cells are often present at inflammation sites. This is the case of endothelial cells of the blood-brain barrier (BBB) of patients afflicted with neurodegenerative disorders such as Alzheimer's, Parkinson's, or multiple sclerosis, as well as in cases of bacterial meningitis, trauma, or tumor-associated ischemia. Inflammation is a known modulator of gene expression through the activation of transcription factors, mostly NF-κB. RLIP76 (a.k.a. RALBP1), an ATP-dependent transporter of electrophile-glutathione conjugates, modulates BBB permeability through the regulation of tight junction function, cell adhesion, and exocytosis. Genes and pathways regulated by RLIP76 are transcriptional targets of tumor necrosis factor alpha (TNF-α) pro-inflammatory molecule, suggesting that RLIP76 may also be an inflammation target. To assess the effects of TNF-α on RLIP76, we faced the problem of choosing reference genes impervious to TNF-α. Since such genes were not known in human BBB endothelial cells, we subjected these to TNF-α, and measured by quantitative RT-PCR the expression of housekeeping genes commonly used as reference genes. We find most to be modulated, and analysis of several inflammation datasets as well as a metaanalysis of more than 5000 human tissue samples encompassing more than 300 cell types and diseases show that no single housekeeping gene may be used as a reference gene. Using three different algorithms, however, we uncovered a reference geneset impervious to TNF-α, and show for the first time that RLIP76 expression is induced by TNF-α and follows the induction kinetics of inflammation markers, suggesting that inflammation can influence RLIP76 expression at the BBB. We also show that MRP1 (a.k.a. ABCC1), another electrophile-glutathione transporter, is not modulated in the same cells and conditions, indicating that RLIP76 regulation by TNF-α is not a general property of glutathione transporters. The reference geneset uncovered herein should aid in future gene expression studies in inflammatory conditions of the BBB.