Discovery and Structure-Activity Relationship Studies of Novel Adenosine A1 Receptor-Selective Agonists.

A series of benzyloxy and phenoxy derivatives of the adenosine receptor agonists N6-cyclopentyl adenosine (CPA) and N6-cyclopentyl 5'-N-ethylcarboxamidoadenosine (CP-NECA) were synthesized, and their potency and selectivity were assessed. We observed that the most potent were the compounds with a halogen in the meta position on the aromatic ring of the benzyloxy- or phenoxycyclopentyl substituent. In general, the NECA-based compounds displayed greater A1R selectivity than the adenosine-based compounds, with N6-2-(3-bromobenzyloxy)cyclopentyl-NECA and N6-2-(3-methoxyphenoxy)cyclopentyl-NECA showing ∼1500-fold improved A1R selectivity compared to NECA. In addition, we quantified the compounds' affinity and kinetics of binding at both human and rat A1R using a NanoBRET binding assay and found that the halogen substituent in the benzyloxy- or phenoxycyclopentyl moiety seems to confer high affinity for the A1R. Molecular modeling studies suggested a hydrophobic subpocket as contributing to the A1R selectivity displayed. We believe that the identified selective potent A1R agonists are valuable tool compounds for adenosine receptor research.

Selective activation of Gαob by an adenosine A1 receptor agonist elicits analgesia without cardiorespiratory depression.

The development of therapeutic agonists for G protein-coupled receptors (GPCRs) is hampered by the propensity of GPCRs to couple to multiple intracellular signalling pathways. This promiscuous coupling leads to numerous downstream cellular effects, some of which are therapeutically undesirable. This is especially the case for adenosine A1 receptors (A1Rs) whose clinical potential is undermined by the sedation and cardiorespiratory depression caused by conventional agonists. We have discovered that the A1R-selective agonist, benzyloxy-cyclopentyladenosine (BnOCPA), is a potent and powerful analgesic but does not cause sedation, bradycardia, hypotension or respiratory depression. This unprecedented discrimination between native A1Rs arises from BnOCPA's unique and exquisitely selective activation of Gob among the six Gαi/o subtypes, and in the absence of ß-arrestin recruitment. BnOCPA thus demonstrates a highly-specific Gα-selective activation of the native A1R, sheds new light on GPCR signalling, and reveals new possibilities for the development of novel therapeutics based on the far-reaching concept of selective Gα agonism.

Management of Home Parenteral Nutrition: Complications and Survival.

BACKGROUND AND AIMS: Parenteral nutrition (PN) has become an efficient, safe, and convenient treatment over years for patients suffering from intestinal failure. Home PN (HPN) enables the patients to have a high quality of life in their own environment. The therapy management however implies many restrictions and potentially severe lethal complications. Prevention and therapy of the latter are therefore of utmost importance. This study aims to assess and characterize the situation of patients with HPN focusing on prevalence of catheter-related complications and mortality. METHODS: Swiss multicentre prospective observational study collecting demographic, anthropometric, and catheter-related data by means of questionnaires every sixth month from 2017 to 2019 (24 months), focusing on survival and complications. Data were analysed using descriptive statistics. Logistic regression models were fitted to investigate association between infection and potential co-factors. RESULTS: Seventy adult patients (50% women) on HPN were included (≈5 patients/million adult inhabitants/year). The most common underlying diseases were cancer (23%), bariatric surgery (11%), and Crohn's disease (10%). The most prevalent indication was short bowel syndrome (30%). During the study period, 47% of the patients were weaned off PN; mortality rate reached 7% for a median treatment duration of 1.31 years. The rate of catheter-related infection was 0.66/1,000 catheter-days (0.28/catheter-year) while the rate of central venous thrombosis was 0.13/1,000 catheter-days (0.05/catheter-year). CONCLUSION: This prospective study gives a comprehensive overview of the adult Swiss HPN patient population. The collected data are prerequisite for evaluation, comparison, and improvement of recommendations to ensure best treatment quality and safety.

Characterization of Novel Fluorescent Bile Salt Derivatives for Studying Human Bile Salt and Organic Anion Transporters.

Bile salts, such as cholate, glycocholate, taurocholate, and glycochenodeoxycholate, are taken up from the portal blood into hepatocytes via transporters, such as the Na+-taurocholate-cotransporting polypeptide (NTCP) and organic anion-transporting polypeptides (OATPs). These bile salts are later secreted into bile across the canalicular membrane, which is facilitated by the bile salt export pump (BSEP). Apart from bile salt transport, some of these proteins (e.g., OATPs) are also key transporters for drug uptake into hepatocytes. In vivo studies of transporter function in patients by using tracer compounds have emerged as an important diagnostic tool to complement classic liver parameter measurements by determining dynamic liver function both for diagnosis and monitoring progression or improvement of liver diseases. Such approaches include use of radioactively labeled bile salts (e.g., for positron emission tomography) and fluorescent bile salt derivatives or dyes (e.g., indocyanine green). To expand the list of liver function markers, we synthesized fluorescent derivatives of cholic and chenodeoxycholic acid by conjugating small organic dyes to the bile acid side chain. These novel fluorescent probes were able to block substrate transport in a concentration-dependent manner of NTCP, OATP1B1, OATP1B3, OATP2B1, BSEP, and intestinal apical sodium-dependent bile salt transporter (ASBT). Whereas the fluorescent bile acid derivatives themselves were transported across the membrane by OATP1B1, OATP1B3, and OATP2B1, they were not transport substrates for NTCP, ASBT, BSEP, and multidrug resistance-related protein 2. Accordingly, these novel fluorescent bile acid probes can potentially be used as imaging agents to monitor the function of OATPs. SIGNIFICANCE STATEMENT: Synthetic modification of common bile acids by attachment of small organic fluorescent dyes to the bile acid side chain resulted in bright, fluorescent probes that interact with hepatic and intestinal organic anion [organic anion-transporting polypeptide (OATP) 1B1, OATP1B3, OATP2B1], bile salt uptake (Na+-taurocholate-cotransporting polypeptide, apical sodium-dependent bile salt transporter), and bile salt efflux (bile salt export pump, multidrug resistance-related protein 2) transporters. Although the fluorescent bile salt derivatives are taken up into cells via the OATPs, the efflux transporters do not transport any of them but one.

Deciphering the Agonist Binding Mechanism to the Adenosine A1 Receptor.

Despite being among the most characterized G protein-coupled receptors (GPCRs), adenosine receptors (ARs) have always been a difficult target in drug design. To date, no agonist other than the natural effector and the diagnostic regadenoson has been approved for human use. Recently, the structure of the adenosine A1 receptor (A1R) was determined in the active, Gi protein complexed state; this has important repercussions for structure-based drug design. Here, we employed supervised molecular dynamics simulations and mutagenesis experiments to extend the structural knowledge of the binding of selective agonists to A1R. Our results identify new residues involved in the association and dissociation pathway, they suggest the binding mode of N6-cyclopentyladenosine (CPA) related ligands, and they highlight the dramatic effect that chemical modifications can have on the overall binding mechanism, paving the way for the rational development of a structure-kinetics relationship of A1R agonists.

The binding orientations of structurally-related ligands can differ; A cautionary note.

Crystal structures can identify ligand-receptor interactions and assist the development of novel therapeutics, but experimental challenges sometimes necessitate the use of homologous proteins. Tropisetron is an orthosteric ligand at both 5-HT3 and α7 nACh receptors and its binding orientation has been determined in the structural homologue AChBP (pdbid: 2WNC). Co-crystallisation with a structurally-related ligand, granisetron, reveals an almost identical orientation (pdbid; 2YME). However, there is a >1000-fold difference in the affinity of tropisetron at 5-HT3 versus α7 nACh receptors, and α7 nACh receptors do not bind granisetron. These striking pharmacological differences prompt questions about which receptor the crystal structures most closely represent and whether the ligand orientations are correct. Here we probe the binding orientation of tropisetron and granisetron at 5-HT3 receptors by in silico modelling and docking, radioligand binding on cysteine-substituted 5-HT3 receptor mutants transiently expressed in HEK 293 cells, and synthetic modification of the ligands. For 15 of the 23 cysteine substitutions, the effects on tropisetron and granisetron were different. Structure-activity relationships on synthesised derivatives of both ligands were also consistent with different orientations, revealing that contrary to the crystallographic evidence from AChBP, the two ligands adopt different orientations in the 5-HT3 receptor binding site. Our results show that even quite structurally similar molecules can adopt different orientations in the same binding site, and that caution may be needed when using homologous proteins to predict ligand binding.

Discovery of Novel Adenosine Receptor Agonists That Exhibit Subtype Selectivity.

A series of N(6)-bicyclic and N(6)-(2-hydroxy)cyclopentyl derivatives of adenosine were synthesized as novel A1R agonists and their A1R/A2R selectivity assessed using a simple yeast screening platform. We observed that the most selective, high potency ligands were achieved through N(6)-adamantyl substitution in combination with 5'-N-ethylcarboxamido or 5'-hydroxymethyl groups. In addition, we determined that 5'-(2-fluoro)thiophenyl derivatives all failed to generate a signaling response despite showing an interaction with the A1R. Some selected compounds were also tested on A1R and A3R in mammalian cells revealing that four of them are entirely A1R-selective agonists. By using in silico homology modeling and ligand docking, we provide insight into their mechanisms of recognition and activation of the A1R. We believe that given the broad tissue distribution, but contrasting signaling profiles, of adenosine receptor subtypes, these compounds might have therapeutic potential.

Management of Home Parenteral Nutrition: A Prospective Multicenter Observational Study.

BACKGROUND: There are no specific Swiss home parenteral nutrition (HPN) data showing patient characteristics, quality of life (QoL) and complications. The goal of this study was to collect representative nationwide data on current adult HPN patients in Switzerland for international comparability and benchmarking. METHODS: This was a multicenter, nationwide, observational study. We conducted interviews for demographics, PN characteristics, QoL and complications. The data were assessed at baseline and after a follow-up of 3 months using a questionnaire. RESULTS: Thirty-three adult patients were included. The most common underlying diseases were cancer, radiation enteritis and state after bariatric surgery, and the most prevalent indication was short bowel syndrome. During the 3-month observation period, significant increase or stabilization of body weight occurred in the patients, physical activity scores improved from 34.0 to 39.4 and mental scores improved from 41.9 to 46.4. HPN dependency and traveling restrictions were of the greatest concern. Diarrhea, xerostomia and/or thirst were frequent complaints. CONCLUSION: Anthropometric parameters and QoL improved during the observational period in this HPN cohort. These Swiss HPN data are prerequisite for evaluation and comparison of HPN recommendations and best clinical practice, status of professional care instructions related to HPN effectiveness, quality of treatment and patient safety.

[Practical scores for the detection of malnutrition]. / Praxisnahe Scores für die Erfassung der Mangelernährung.

Malnutrition occurs in 30 - 60 % of hospitalized medical or surgical patients, as well as out-patients. Serious consequences at various levels were observed. Malnutrition influences negatively the quality of life, the immune system, muscle strength and worsens the prognosis of the patient. Interventions for a rapid and simple identification and effective treatment of this condition are essential and cost saving. Screening tools for the identification of patients at nutritional risk are very useful in daily practice. The systematic identification of patients with potential or apparent malnutrition is very important allowing an effective nutritional treatment at an early time. The medical team in charge should perform the nutritional risk screening and the following assessment to recognize the nutritional problems and to solve them in an interdisciplinary and -professional team.

Design, synthesis and pharmacological characterization of analogs of 2-aminoethyl diphenylborinate (2-APB), a known store-operated calcium channel blocker, for inhibition of TRPV6-mediated calcium transport.

2-Aminoethyl diphenylborinate (2-APB) is a known modulator of the IP3 receptor, the calcium ATPase SERCA, the calcium release-activated calcium channel Orai and TRP channels. More recently, it was shown that 2-APB is an efficient inhibitor of the epithelial calcium channel TRPV6 which is overexpressed in prostate cancer. We have conducted a structure-activity relationship study of 2-APB congeners to understand their inhibitory mode of action on TRPV6. Whereas modifying the aminoethyl moiety did not significantly change TRPV6 inhibition, substitution of the phenyl rings of 2-APB did. Our data show that the diaryl borinate moiety is required for biological activity and that the substitution pattern of the aryl rings can influence TRPV6 versus SOCE inhibition. We have also discovered that 2-APB is hydrolyzed and transesterified within minutes in solution.

[Sausage or carrot--spoilt for choice]. / Cervelat oder rüebli--die qual der wahl!

As far as healthy food is concerned, it cannot be categorized simply as "good" or "bad" since its effect on health depends mainly on the amount and method consumed. Today's recommendations include a diversified diet, a diet which targets energy-balance and provides all nutrients necessary. Living in an affluent society aggravates healthy choices because of a constantly available, large assortment of food items. In general, the way food is prepared these days has changed a lot: mainly, the energy content has constantly increased, while the fiber and natural micronutrient concentrations decreased. Food items with a high energy yield, containing a lot of fat and sugar, affects our energy balance, which may lead to diseases of affluence such as type 2 diabetes, cardiovascular diseases, and some kinds of tumors.

Nutritional screening tools in daily clinical practice: the focus on cancer.

INTRODUCTION: Malnutrition is a common and under-recognized problem in cancer patients. It has been correlated to a large number of physical, psychological, and clinically relevant adverse effects in oncology patients, including impaired tolerance to anticancer therapy, adverse reactions, and reduced quality of life. Consequently, tailored strategies to identify patients at nutritional risk are essential to implement nutritional support effectively and to reduce cancer morbidity. PURPOSE OF A NUTRITIONAL SCREENING TOOL: A screening tool should be an easy, standardized, rapid, noninvasive, and cost-effective diagnostic tool to identify cancer patients at nutritional risk in daily clinical practice. If patients at risk for malnutrition are identified early, many cases may be treated or prevented, with beneficial effects on patient outcome and subsequent reductions of health care costs. SCREENING TOOLS: This article discusses the Malnutrition Universal Screening Tool, the Nutritional Risk Screening, the Mini Nutritional Assessment--Short Form, the scored Patient-Generated Subjective Global Assessment (PG-SGA), and the Malnutrition Screening Tool (MST) in an oncology setting. CONCLUSIONS: Clinical institutions should implement an appropriate and validated screening tool and assessment protocol, which should contain an action plan. To date, the MST and the PG-SGA are the best validated screening tools for use in oncology patients. The PG-SGA is an assessment tool with screening components, whereas the MST is a pure screening tool and, therefore, quick and easy to use for trained as well as untrained staff. Further validation of all nutrition screening tools is needed, as well as further research to evaluate the benefits of nutrition screening and support with regard to outcomes.