Evaluating interactions between the melanocortin-5 receptor, MRAP1, and ACTH(1-24): A phylogenetic study.

The melanocortin-2 receptor (MC2R) and the melanocortin-5 receptor (MC5R) are found on the same chromosome in most vertebrate genomes, and for the species analyzed in this study, MC2R and MC5R are co-expressed in glucocorticoid-producing cells that also express the accessory protein MRAP1. Since MRAP1 affects the ligand sensitivity of MC2R orthologs, this study tested the hypothesis that co-expression of MC5R with MRAP1 would also affect the ligand sensitivity of MC5R. The hypothesis was confirmed for stingray, rainbow trout, and chicken, MC5R orthologs. However, elephant shark MC5R was not affected in the same way by co-expression of MRAP1. It appears that, for some MC5R orthologs (i.e., stingray, rainbow trout, and chicken), a docking site for the R/KKRRP motif of ACTH(1-24) may become exposed on the receptor following co-expression with MRAP1. However, for elephant shark MC5R co-expression with MRAP1 may not affect engagement ACTH(1-24). Hence during the radiation of the chordates, the interaction between MRAP1 and MC5R has diverged.

Analyzing the effects of co-expression of chick (Gallus gallus) melanocortin receptors with either chick MRAP1 or MRAP2 in CHO cells on sensitivity to ACTH(1-24) or ACTH(1-13)NH2: Implications for the avian HPA axis and avian melanocortin circuits in the hypothalamus.

In order to better understand the roles that melanocortin receptors (cMCRs) and melanocortin-2 receptor accessory proteins (cMRAP1 and cMRAP2) play in the HPA axis and hypothalamus, adrenal gland and hypothalamus mRNA from 1day-old white leghorn chicks (Gallus gallus), were analyzed by real-time PCR. mRNA was also made for kidney, ovary, and liver. Mrap1 mRNA could be detected in adrenal tissue, but not in any of the other tissues, and mrap2 mRNA was also detected in the adrenal gland. Finally, all five melanocortin receptors mRNAs could be detected in the adrenal gland; mc2r and mc5r mRNAs were the most abundant. To evaluate any potential interactions between MRAP1 and the MCRs that may occur in adrenal cells, individual chick mcr cDNA constructs were transiently expressed in CHO cells either in the presence or absence of a chick mrap1 cDNA, and the transfected cells were stimulated with hACTH(1-24) at concentrations ranging from 10-13M to 10-6M. As expected, MC2R required co-expression with MRAP1 for functional expression; whereas, co-expression of cMC3R with cMRAP1 had no statistically significant effect on sensitivity to hACTH(1-24). However, co-expression of MC4R and MC5R with MRAP1, increased sensitivity for ACTH(1-24) by approximately 35 fold and 365 fold, respectively. However, co-expressing of cMRAP2 with these melanocortin receptors had no effect on sensitivity to hACTH(1-24). Since the real-time PCR analysis detected mrap2 mRNA and mc4r mRNA in the hypothalamus, the interaction between cMC4R and cMRAP2 with respect to sensitivity to ACTH(1-13)NH2 stimulation was also evaluated. However, no effect, either positive or negative, was observed. Finally, the highest levels of mc5r mRNA were detected in liver cells. This observation raises the possibility that in one-day old chicks, activation of the HPA axis may also involve a physiological response from liver cells.

Efficacy of empiric antibiotic management of septic olecranon bursitis without bursal aspiration in emergency department patients.

OBJECTIVES: Many guidelines for septic olecranon bursitis recommend aspiration of the bursa prior to initiation of antimicrobial therapy despite the absence of robust clinical data to support this practice and known risk of aspiration complications. Our objective was to describe outcomes associated with empiric antibiotic therapy without bursal aspiration among emergency department (ED) patients with suspected septic olecranon bursitis. METHODS: We conducted a retrospective observational cohort study of patients presenting to an academic ED from January 1, 2011, to December 31, 2018, with olecranon bursitis. The health record was reviewed to assess patient characteristics and outcomes within 6 months of the ED visit. Olecranon bursitis was considered "suspected septic" if the patient was treated with antibiotics. The primary outcome of interest was complicated versus uncomplicated bursitis resolution. Uncomplicated resolution was defined as bursitis resolution without subsequent bursal aspiration, surgery, or hospitalization. RESULTS: During the study period, 264 ED patients were evaluated for 266 cases of olecranon bursitis. The median age was 57 years and 85% were men. Four (1.5%) patients had bursal aspiration during their ED visit, 39 (14.7%) were admitted to the hospital, 76 (28.6%) were dismissed without antibiotic therapy, and 147 (55.3%) were dismissed with empiric antibiotic therapy for suspected septic olecranon bursitis. Among these 147 patients, 134 had follow-up available including 118 (88.1%, 95% confidence interval [CI] = 81.1%-92.8%) with an uncomplicated resolution, eight (6.0%, 95% CI = 2.8%-11.8%) who underwent subsequent bursal aspiration, and nine (6.7%, 95% CI = 3.3%-12.7%) who were subsequently admitted for inpatient antibiotics. CONCLUSIONS: Eighty-eight percent of ED patients with suspected septic olecranon bursitis treated with empiric antibiotics without aspiration had resolution without need for subsequent bursal aspiration, hospitalization, or surgery. Our findings suggest that empiric antibiotics without bursal aspiration may be a reasonable initial approach to ED management of select patients with suspected septic olecranon bursitis.

Coronary Artery Disease in Adults With Coarctation of Aorta: Incidence, Risk Factors, and Outcomes.

Background Premature coronary artery disease ( CAD ) is common in patients with coarctation of aorta ( COA ), but there are limited data about any direct relationship (or lack thereof) between COA and CAD . We hypothesized that atherosclerotic cardiovascular disease risk factors, rather than COA diagnosis, was the primary determinant of CAD occurrence in patients with COA . Methods and Results This is a retrospective study of 654 COA patients and a control group of 876 patients with valvular pulmonic stenosis and tetralogy of Fallot to determine prevalence and independent risk factors for CAD . There was no evidence of a difference in the unadjusted CAD prevalence between the COA and control groups (7.8% versus 6.3%, P=0.247), but premature CAD was more common in COA patients (4.4% versus 1.8%, P=0.002). In the analysis of a propensity-matched cohort of 126 COA and 126 control patients, there was no evidence of a difference in overall CAD prevalence (6.3% versus 5.6% versus P=0.742) and premature CAD prevalence (4.8% versus 3.2%, P=0.518). The multivariable risk factors for CAD were hypertension (odds ratio [ OR ] 2.14; 95% CI 1.36-3.38), hyperlipidemia ( OR 3.33; 95% CI 2.02-5.47), diabetes mellitus ( OR 1.98; 95% CI 1.31-3.61), male sex ( OR 2.05; 95% CI 1.33-3.17), and older age per year ( OR 1.06; 95% CI 1.04-1.07). Conclusions After adjusting for atherosclerotic cardiovascular disease risk factors, we did not find evidence of a difference in CAD risk between the patients with COA and other patients with congenital heart disease.

60 YEARS OF POMC: Melanocortin receptors: evolution of ligand selectivity for melanocortin peptides.

The evolution of the melanocortin receptors (MCRs) is linked to the evolution of adrenocorticotrophic hormone (ACTH), the melanocyte-stimulating hormones (MSHs), and their common precursor pro-opiomelanocortin (POMC). The origin of the MCRs and POMC appears to be grounded in the early radiation of the ancestral protochordates. During the genome duplications that have occurred during the evolution of the chordates, the organization plan for POMC was established, and features that have been retained include, the high conservation of the amino acid sequences of α-MSH and ACTH, and the presence of the HFRW MCR activation motif in all of the melanocortin peptides (i.e. ACTH, α-MSH, ß-MSH, γ-MSH, and δ-MSH). For the MCRs, the chordate genome duplication events resulted in the proliferation of paralogous receptor genes, and a divergence in ligand selectivity. While most gnathostome MCRs can be activated by either ACTH or the MSHs, teleost and tetrapod MC2R orthologs can only be activated by ACTH. The appearance of the accessory protein, MRAP1, paralleled the emergence of teleost and tetrapods MC2R ligand selectivity, and the dependence of these orthologs on MRAP1 for trafficking to the plasma membrane. The accessory protein, MRAP2, does not affect MC2R ligand selectivity, but does influence the functionality of MC4R orthologs. In this regard, the roles that these accessory proteins may play in the physiology of the five MCRs (i.e. MC1R, MC2R, MC3R, MC4R, and MC5R) are discussed.