Structural basis for CCR6 modulation by allosteric antagonists.

The CC chemokine receptor 6 (CCR6) is a potential target for chronic inflammatory diseases. Previously, we reported an active CCR6 structure in complex with its cognate chemokine CCL20, revealing the molecular basis of CCR6 activation. Here, we present two inactive CCR6 structures in ternary complexes with different allosteric antagonists, CCR6/SQA1/OXM1 and CCR6/SQA1/OXM2. The oxomorpholine analogues, OXM1 and OXM2 are highly selective CCR6 antagonists which bind to an extracellular pocket and disrupt the receptor activation network. An energetically favoured U-shaped conformation in solution that resembles the bound form is observed for the active analogues. SQA1 is a squaramide derivative with close-in analogues reported as antagonists of chemokine receptors including CCR6. SQA1 binds to an intracellular pocket which overlaps with the G protein site, stabilizing a closed pocket that is a hallmark of inactive GPCRs. Minimal communication between the two allosteric pockets is observed, in contrast to the prevalent allosteric cooperativity model of GPCRs. This work highlights the versatility of GPCR antagonism by small molecules, complementing previous knowledge of CCR6 activation, and sheds light on drug discovery targeting CCR6.

Small molecule branched-chain ketoacid dehydrogenase kinase (BDK) inhibitors with opposing effects on BDK protein levels.

Branched chain amino acid (BCAA) catabolic impairments have been implicated in several diseases. Branched chain ketoacid dehydrogenase (BCKDH) controls the rate limiting step in BCAA degradation, the activity of which is inhibited by BCKDH kinase (BDK)-mediated phosphorylation. Screening efforts to discover BDK inhibitors led to identification of thiophene PF-07208254, which improved cardiometabolic endpoints in mice. Structure-activity relationship studies led to identification of a thiazole series of BDK inhibitors; however, these inhibitors did not improve metabolism in mice upon chronic administration. While the thiophenes demonstrated sustained branched chain ketoacid (BCKA) lowering and reduced BDK protein levels, the thiazoles increased BCKAs and BDK protein levels. Thiazoles increased BDK proximity to BCKDH-E2, whereas thiophenes reduced BDK proximity to BCKDH-E2, which may promote BDK degradation. Thus, we describe two BDK inhibitor series that possess differing attributes regarding BDK degradation or stabilization and provide a mechanistic understanding of the desirable features of an effective BDK inhibitor.

Indian Perspective of Burnout Among Plastic Surgeons.

Introduction Over the last decade, the term "Burnout" has become familiar term in all walks of life, particularly medicine. Emotional exhaustion, depersonalization, and a low sense of personal accomplishment make up the triad. At least a third of plastic surgeons are having burnout according to the western literature. Data on burnout in Indian plastic surgeons is lacking. We have made an attempt to analyze the incidence and factors responsible for burnout among plastic surgeons in India. Materials and Methods An online survey was conducted in India to assess burnout among plastic surgeons from June to November 2019. Consent, demographic information, stress-related factors, the abbreviated Maslach Burnout Inventory (aMBI), and Satisfaction with Medicine were all included section wise in the survey. Both used scales were validated. Data were gathered using Google forms, then uploaded to an Excel file and analyzed. A multivariable and univariable analysis of factors associated with burnout was carried out. Results Twenty-two percent of 330 plastic surgeons who responded were assessed to have moderate to high emotional exhaustion, 5% had moderate to high depersonalization, and 3% had low personal accomplishment. The overall burnout rate was 8.2%. Seventy-three percent of plastic surgeons enjoyed a good to very good quality of life. Great over-volume of work, mid-career practicing plastic surgeons and professional satisfaction with work were found to have a significant association with burnout on multivariate analysis. Conclusions Plastic surgeons in India suffer an overall burnout rate of 8.2% with a multifactorial etiology. This occupational hazard is preventable and reversible. Plastic surgeons need to be vigilant about this and seek help whenever required.

Structural studies identify angiotensin II receptor blocker-like compounds as branched-chain ketoacid dehydrogenase kinase inhibitors.

The mammalian mitochondrial branched-chain ketoacid dehydrogenase (BCKD) complex is a multienzyme complex involved in the catabolism of branched-chain amino acids. BCKD is regulated by the BCKD kinase, or BCKDK, which binds to the E2 subunit of BCKD, phosphorylates its E1 subunit, and inhibits enzymatic activity. Inhibition of the BCKD complex results in increased levels of branched-chain amino acids and branched-chain ketoacids, and this buildup has been associated with heart failure, type 2 diabetes mellitus, and nonalcoholic fatty liver disease. To find BCKDK inhibitors for potential treatment of these diseases, we performed both NMR and virtual fragment screening and identified tetrazole-bearing fragments that bind BCKDK at multiple sites. Through structure-based virtual screening expanding from these fragments, the angiotensin receptor blocker class antihypertension drugs and angiotensin receptor blocker-like compounds were discovered to be potent BCKDK inhibitors, suggesting potential new avenues for heart failure treatment combining BCKDK inhibition and antihypertension.

Discovery of High-Affinity Small-Molecule Binders of the Epigenetic Reader YEATS4.

A series of small-molecule YEATS4 binders have been discovered as part of an ongoing research effort to generate high-quality probe molecules for emerging and/or challenging epigenetic targets. Analogues such as 4d and 4e demonstrate excellent potency and selectivity for YEATS4 binding versus YEATS1,2,3 and exhibit good physical properties and in vitro safety profiles. A new X-ray crystal structure confirms direct binding of this chemical series to YEATS4 at the lysine acetylation recognition site of the YEATS domain. Multiple analogues engage YEATS4 with nanomolar potency in a whole-cell nanoluciferase bioluminescent resonance energy transfer assay. Rodent pharmacokinetic studies demonstrate the competency of several analogues as in vivo-capable binders.

Management of Posttraumatic Posterior Elbow Defects by Nonmicrosurgical Reconstruction.

Introduction Reconstruction of posterior defects is challenging due to the quality and uniqueness of the excess skin at the elbow that is durable, thick, pliable, and without much subcutaneous tissue. The goal of reconstruction is to cover the elbow defects with a durable skin cover that will facilitate full passive range of motion. In this era of microsurgery, free tissue transfer is feasible for almost any defect. However, in this article, we discuss various locoregional and pedicled flap options and the protocol followed at our institute to tackle posttraumatic posterior elbow defects. Materials and Methods This is a retrospective analysis of 48 patients with posttraumatic posterior elbow defects admitted from January 2012 to February 2020. Posterior elbow defects were assessed according to the size and location and managed with a nonmicrosurgical reconstruction. Results Of 48 patients, 32 were managed with nonmicrosurgical flaps. Eighteen patients had large defects and 14 had small defects. Reverse lateral forearm flap was the workhorse flap for defect coverage. Of 32 flaps, nine developed complications; however, no patient had total flap necrosis. Conclusion Posterior elbow defects are a difficult problem to tackle. To achieve optimal results, all patients with elbow trauma should be attended and managed by orthopaedic and plastic surgeons in collaboration for optimal results. We believe that most of these defects can be resurfaced by nonmicrosurgical reconstruction with proper planning and execution and their utility cannot be understated.

Nuances of Arteriovenous Fistula Creation for Vascular Access in Hemodialysis.

Background With rising incidence and increased life expectancy of patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD), the number of patients requiring hemodialysis has increased substantially. Vascular access is the lifeline for a patient on hemodialysis (HD), and an arteriovenous fistula (AVF) is the undisputed gold standard for HD access. An effective and long-lasting fistula serves to increase the life expectancy of ESRD patients and improves their quality of life. Learning Objectives This paper aims to give a comprehensive overview of AVF creation, including the various techniques, patient selection, troubleshooting with decision-making, and common complications. Authors share their experience from previous publications and over 2000 AVF surgeries. They have not only described a new modification of the technique of proximal fistula but have also established a direct correlation between bruit and thrill on operation table and success of fistula surgery. Conclusion A standardized, protocol-driven multidisciplinary approach with careful patient and site selection, guided by outcome predictors, is vital in AVF surgery. Knowledge about the potential complications of AVFs contributes to their timely detection and allows measures to be taken that might prevent deleterious consequences that range from loss of vascular access to serious morbidity and mortality.

Post-CABG Deep Sternal Wound Infection: A Retrospective Comparative Analysis of Early versus Late Referral to a Plastic Surgery Unit in a Tertiary Care Center.

Background Deep sternal wound infections (DSWI) following median sternotomy are initially treated by the cardiothoracic surgeons and are referred to a plastic surgical unit late in the course of time. Methods This is a retrospective review done in a tertiary care teaching institute from January 2005 to June 2018 and the data of 72 patients who had DSWI out of 4,214 patients who underwent median sternotomy for coronary artery bypass grafting (CABG) was collected with respect to the duration between CABG and presentation of DSWI as well as time of referral to a plastic surgery unit. We defined early referral as < or equal to 15 days from presentation and late referral as > 15 days. Both groups were compared with respect to multiple parameters as well as early and late postoperative course, postoperative complications, and mortality. Results The early group had 33 patients, while the late group had 39 patients. The number of procedures done by the cardiothoracic team before referral to the plastic surgery unit is significant ( p = 0.002). The average duration from the presentation of DSWI to definitive surgery was found to be 16.58 days in the early group and 89.36 days in the late group. The rest of the variables that were compared in both the groups did not have significant differences. Conclusion There is no statistical difference between early and late referral to plastic surgery in terms of mortality and morbidity. Yet, early referrals could lead to highly significant reduction in total duration of hospital stay, wound healing, and costs. Early referral of post-CABG DSWIs to Plastic surgeons by the cardiothoracic surgeons is highly recommended.

Toward the assembly and characterization of an encoded library hit confirmation platform: Bead-Assisted Ligand Isolation Mass Spectrometry (BALI-MS).

The ability to predict chemical structure from DNA sequence has to date been a necessary cornerstone of DNA-encoded library technology. DNA-encoded libraries (DELs) are typically screened by immobilized affinity selection and enriched library members are identified by counting the number of times an individual compound's sequence is observed in the resultant dataset. Those with high signal reads (DEL hits) are subsequently followed up through off-DNA synthesis of the predicted small molecule structures. However, hits followed-up in this manner often fail to translate to confirmed ligands. To address this low conversion rate of DEL hits to off-DNA ligands, we have developed an approach that eliminates the reliance on chemical structure prediction from DNA sequence. Here we describe our method of combining non-combinatorial resynthesis on-DNA following library procedures as a rapid means to assess the probable molecules attached to the DNA barcode. Furthermore, we apply our Bead-Assisted Ligand Isolation Mass Spectrometry (BALI-MS) technique to identify the true binders found within the mixtures of on-DNA synthesis products. Finally, we describe a Normalized Enrichment (NE) metric that allows for the quantitative assessment of affinity selection in these studies. We exemplify how this combined approach enables the identification of putative hit matter against a clinically relevant therapeutic target bisphosphoglycerate mutase, BPGM.