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Background: Thoracic aortic dissection (TAD) is a silent killer. Approximately two-thirds of the cases occur in the ascending aorta (i.e. type A dissection) and majority of them are unrelated to genetic mutations. However, animal models of spontaneous type A dissection are not widely available. In the present study, a novel mouse TAD model was created. Further, the role of gasdermin D (GSDMD) in TAD development was evaluated. Methods: TADs were created by treating ascending aorta of adult mice (C57BL/6J) with active elastase (40.0 U/ml) and ß-aminopropionitrile (Act E+BAPN). The temporal progress of the TAD pathology was rigorously characterized by histological evaluation and scanning electron microscopy, while potential mechanisms explored with bulk RNA sequencing of specimens collected at multiple timepoints. With this novel TAD model, further experiments were performed with Gsdmd -/- mice to evaluate its impact on TAD formation. Results: The ascending aorta challenged with Act E+BAPN developed pathology characterized by an early onset of intimomedial tears (complete penetration) and intramural hematoma, followed by progressive medial loss and aortic dilation. Ingenuity Pathway Analysis and functional annotation of differentially expressed genes suggested that a unique inflammatory micro-environment, rather than general inflammation, promoted the onset of TADs by specifically recruiting neutrophils to the aortic wall, while the pathology at the advanced stage was driven by T-cell mediated immune injury. Gsdmd -/- attenuated medial loss, adventitial fibrosis, and dilation of TADs. This protective effect was associated with a reduced number of TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) positive cells and T-cells in TADs. Conclusions: A novel mouse TAD model was created in the ascending aorta. It produces a unique microenvironment to activate different immune cell subsets, promoting onset and subsequent remodeling of TADs. Consistently, Gsdmd -/- attenuates TAD development, with modulation of cell death and T-cell response likely acting as the underlying mechanism.

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ß-Defensin 3 (BD3) was identified as a ligand for the melanocortin receptors (MCRs) in 2007, although the pharmacology activity of BD3 has not been clearly elucidated. Herein, it is demonstrated that human BD3 and mouse BD3 are full micromolar agonists at the MCRs. Furthermore, mouse ß-defensin 1 (BD1) and human BD1 are also MCR micromolar agonists. This work identifies BD1 as an endogenous MCR ligand and clarifies the controversial role of BD3 as a micromolar agonist.

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The melanocortin system is involved in the regulation of several complex physiological functions. In particular, the melanocortin-3 and -4 receptors (MC3R/MC4R) have been demonstrated to regulate body weight, energy homeostasis, and feeding behavior. Synthetic and endogenous melanocortin agonists have been shown to be anorexigenic in rodent models. Herein, we report synthesis and structure-activity relationship (SAR) studies of 27 nonpeptide small molecule ligands based on an unsymmetrical substituted urea core. Three templates containing key residues from the lead compounds, showing diversity at three positions (R(1), R(2), R(3)), were designed and synthesized. The syntheses were optimized for efficient microwave-assisted chemistry that significantly reduced total syntheses time compared to a previously reported room temperature method. The pharmacological characterization of the compounds on the mouse melanocortin receptors identified compounds 1 and 12 with full agonist activity at the mMC4R, but no activity was observed at the mMC3R when tested up to 100 µM concentrations. The SAR identified compounds possessing aliphatic or saturated cyclic amines at the R(1) position, bulky aromatic groups at the R(2) position, and benzyl group at the R(3) position resulted in mMC4R selectivity over the mMC3R. The small molecule template and SAR knowledge from this series may be helpful in further design of MC3R/MC4R selective small molecule ligands.

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The multiple beneficial effects of calorie restriction (CR) on several organs, including the heart, are widely known. Recently, the plant polyphenol resveratrol has been shown to possess several beneficial effects similar to those of CR. Among the host of effects on cardiac muscle, a cellular self-eating process called autophagy has been shown to be induced by both CR and resveratrol. Autophagy is vital in removing dysfunctional organelles and damaged proteins from the cell, thereby maintaining cellular quality control. In this study, we explored whether short-term moderate CR (20%), either alone or in combination with resveratrol, can induce autophagy in the hearts of 26-month-old Fischer 344 × Brown Norway rats. Autophagy stimulation was investigated by measuring the protein expression levels of the autophagy proteins beclin-1, Atg5, and p62 and the LC3-II/LC3-I ratio. We found that 20% CR or resveratrol alone for 6 weeks could not induce autophagy, but 20% CR in combination with 50 mg/kg/day resveratrol resulted in an induction of autophagy in the hearts of 26-month-old rats. Although oxidative stress has been proposed to be an inducer of autophagy, treatment with the chemotherapeutic drug doxorubicin was unable to stimulate autophagy. The enhanced autophagy due to CR + resveratrol was associated with protection from doxorubicin-induced damage, as measured by cardiac apoptotic levels and serum creatine kinase and lactate dehydrogenase activity. We propose that a combinatorial approach of low-dose CR and resveratrol has the potential to be used therapeutically to induce autophagy and provides protection against doxorubicin-mediated toxicity.

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