Superagonism at G protein-coupled receptors and beyond.

Ligands targeting GPCRs can be categorized according to their intrinsic efficacy to trigger a specific, receptor-mediated response. A ligand endowed with the same level of efficacy as the endogenous agonist can be classified as a full agonist, whereas a compound that displays greater efficacy, that is, higher receptor signalling output than the endogenous agonist, can be called a superagonist. Subsequent to GPCR activation, an intracellular signalling cascade is set in motion, which may generate substantial amplification of the signal. This may obscure superagonism in pharmacological assays and, therefore, the definition of superagonism necessitates a combination of operational approaches, reduction of spare receptors or estimation of receptor activation close to the receptor level to quantify relative agonist efficacies in a particular system. The first part of this review will compare GPCR superagonism with superagonism in the field of immunology, where this term is well established. In the second part, known GPCR superagonists will be reviewed. Then, the experimental and analytical challenges in the deconvolution of GPCR superagonism will be addressed. Finally, the potential benefit of superagonism is discussed. The molecular mechanisms behind GPCR superagonism are not completely understood. However, crystallography shows that agonist binding alone is not sufficient for a fully active receptor state and that binding of the G protein is at least equally important. Accordingly, the emerging number of reported superagonists implies that ligand-induced receptor conformations more active than the ones stabilized by the endogenous agonist are indeed feasible. Superagonists may have therapeutic potential when receptor function is impaired or to induce negative feedback mechanisms. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

[Health-related quality of life in patients with chronic kidney disease]. / Qualita' della vita nei nefropatici.

Assessment of quality of life in patients with different degrees of chronic kidney disease is an important issue because of its impact on clinical decisions and financial resource management in the health-care system. The aim of this study was to assess whether a generic instrument like the SF-36 questionnaire is able to discriminate three different populations of patients with different degrees of renal disease (pre-ESRD, ESRD, TxR). Five hundred sixty-three patients from 12 Italian nephrology units completed the SF-36 scales by themselves. The results from these samples were compared with those from the general population. Univariate analysis and multivariate regression were used. The generic SF-36 questionnaire proved to be a powerful instrument to discriminate populations with different degrees of chronic renal failure. The quality of life of patients on dialysis is significantly worse than that of the normal population and other patients with less severe renal function impairment.

[Acute biocompatibility of hemodiafiltration with endogenous reinfusion (HFR)]. / Emodiafiltrazione con reinfusione endogena (HFR): profilo di biocompatibilità in acuto.

PURPOSE: In order to reduce the hemodialysis (HD)-induced pro-inflammatory activity we need to use a biocompatible dialysis membrane, avoid backfiltration and possibly use adsorbents. Hemodiafiltration reinfusion (HFR) is a new on-line hemodiafiltration (HDF) technique combining these aspects. This study aimed to evaluate the biocompatibility of the single dialysis session comparing standard HD and HFR. METHODS: Eighteen patients on chronic HD were enrolled in five Centers. Patients underwent one standard and two HFR study sessions; in each session we evaluated leukocyte activation at 0, 5, 15, 60 and 240 min; and interleukin-6 (IL-6), C-reactive protein (CRP) and IL-1 receptor antagonist (IL-1Ra) levels at 0, 60 and 240 min. RESULTS: Leukocyte activation was similar in HD and HFR, while the post-dialysis IL-6 increase was lower with HFR; CRP levels were stable during HFR, but increased after HD, and IL-1Ra did not demonstrate any difference. CONCLUSIONS: These preliminary data show that HFR still has a better biocompatibility in the single dialysis session.

Polymorphism of the angiotensin-converting enzyme gene in end-stage renal failure patients.

The plasma levels of angiotensin-converting enzyme (ACE) are modulated by the insertion (I)/deletion (D) polymorphism within the ACE gene locus. An association between progressive renal disease, raised cardiovascular risk, and ACE plasma levels has been shown. To evaluate the genotype frequencies of the I/D polymorphism in terminal renal failure, we have enrolled 341 dialysis patients (321 on hemodialysis and 20 on peritoneal dialysis) in a district of southern Italy (Foggia). As controls, 1,307 subjects from the same area have been enrolled. Genomic DNA was obtained from leukocytes, and the ACE I/D polymorphism was determined by polymerase chain reaction. Among uremics, 151 subjects (44.3%) carried the DD genotype, 149 (43.7%) the ID, and 41 (12.0%) the II genotype. In controls, 560 subjects (42.8%) had the DD genotype, 577 (44.1%) the ID, and 170 (13.1%) the II genotype (p = n.s.). Among patients, the frequency of DD subjects was higher in men (48.3%) than in women (39. 7%, p < 0.01). A slight different frequency of the DD genotype was found according to the duration of dialysis treatment: 47.5% in patients on dialysis up to 60 months and 41.7 and 40.6% in those with a dialytic age of 60-120 and >120 months, respectively (p for trend: 0.53). Patients with or without cardiovascular diseases, such as hypertension, left ventricular hypertrophy, coronary artery disease, and chronic cardiac failure, did not exhibit any difference in ACE I/D allele and genotype frequencies (p always >0.05). In conclusion, frequencies of the ACE DD genotype were similar in uremics and in controls and did not differ between patients with and without cardiovascular diseases. A nonsignificant inverse relationship with the time spent on dialysis was observed, suggesting that ACE I/D polymorphism may influence the cardiovascular death rate.

Extensive 200-million-year-Old continental flood basalts of the central atlantic magmatic province

The Central Atlantic Magmatic Province (CAMP) is defined by tholeiitic basalts that crop out in once-contiguous parts of North America, Europe, Africa, and South America and is associated with the breakup of Pangea. 40Ar/39Ar and paleomagnetic data indicate that CAMP magmatism extended over an area of 2.5 million square kilometers in north and central Brazil, and the total aerial extent of the magmatism exceeded 7 million square kilometers in a few million years, with peak activity at 200 million years ago. The magmatism coincided closely in time with a major mass extinction at the Triassic-Jurassic boundary.