Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

X-ray crystal structure of the ancestral 3-ketosteroid receptor-progesterone-mifepristone complex shows mifepristone bound at the coactivator binding interface.

Steroid receptors are a subfamily of nuclear receptors found throughout all metazoans. They are highly important in the regulation of development, inflammation, and reproduction and their misregulation has been implicated in hormone insensitivity syndromes and cancer. Steroid binding to SRs drives a conformational change in the ligand binding domain that promotes nuclear localization and subsequent interaction with coregulator proteins to affect gene regulation. SRs are important pharmaceutical targets, yet most SR-targeting drugs have off-target pharmacology leading to unwanted side effects. A better understanding of the structural mechanisms dictating ligand specificity and the evolution of the forces that created the SR-hormone pairs will enable the design of better pharmaceutical ligands. In order to investigate this relationship, we attempted to crystallize the ancestral 3-ketosteroid receptor (ancSR2) with mifepristone, a SR antagonist. Here, we present the x-ray crystal structure of the ancestral 3-keto steroid receptor (ancSR2)-progesterone complex at a resolution of 2.05 Å. This improves upon our previously reported structure of the ancSR2-progesterone complex, permitting unambiguous assignment of the ligand conformation within the binding pocket. Surprisingly, we find mifepristone, fortuitously docked at the protein surface, poised to interfere with coregulator binding. Recent attention has been given to generating pharmaceuticals that block the coregulator binding site in order to obstruct coregulator binding and achieve tissue-specific SR regulation independent of hormone binding. Mifepristone's interaction with the coactivator cleft of this SR suggests that it may be a useful molecular scaffold for further coactivator binding inhibitor development

Overall structure of the ancSR2–progesterone–mifepristone complex.

<p>Overall structure of the ancSR2 LBD with bound progesterone and mifepristone shown as green and magenta, respectively with oxygens, colored red. Helices are blue, β-sheets are yellow, loops are white. Figures were generated in PyMol (Schödenger, LLC).</p

Mifepristone and 4-hydroxytamoxifen show similar binding modes to the steroid receptor coactivator binding cleft.

<p>Alignment of the ancSR2–progesterone–mifepristone crystal structure and the ERβ–tamoxifen structure shows both mifepristone and 4-hydroxytamoxifen bound to the coactivator cleft. ancSR2 – slate blue, mifepristone – magenta, ERβ – light green, tamoxifen – orange.</p

Mifepristone binding site interactions.

<p>ancSR2 is shown in slate blue; mifepristone is shown in magenta (oxygens, red; nitrogens, blue). Residues within 4.2 Å of the ligand are shown. A. Site-one mifepristone interacts with both the monomer in the asymmetric unit as well as residues in a symmetry mate (forest green). B. Site-two mifepristone interacts with residues in the ancSR2 coactivator cleft. </p

Crystals of the ancSR2–progesterone–mifepristone complex and <i>in</i><i>vitro</i> activation data.

<p>A. The ancSR2–progesterone–mifepristone ternary complex crystals measured approximately 50 x 20 x 20 microns. B. In luciferase reporter assays, ancSR2 is strongly activated by mifepristone (EC₅₀ = 56 ± 1.2 nM) as well as progesterone (EC₅₀ = 78 ± 1.7 pM). </p

Evolution of Minimal Specificity and Promiscuity in Steroid Hormone Receptors

Most proteins are regulated by physical interactions with other molecules; some are highly specific, but others interact with many partners. Despite much speculation, we know little about how and why specificity/promiscuity evolves in natural proteins. It is widely assumed that specific proteins evolved from more promiscuous ancient forms and that most proteins' specificity has been tuned to an optimal state by selection. Here we use ancestral protein reconstruction to trace the evolutionary history of ligand recognition in the steroid hormone receptors (SRs), a family of hormone-regulated animal transcription factors. We resurrected the deepest ancestral proteins in the SR family and characterized the structure-activity relationships by which they distinguished among ligands. We found that that the most ancient split in SR evolution involved a discrete switch from an ancient receptor for aromatized estrogens—including xenobiotics—to a derived receptor that recognized non-aromatized progestagens and corticosteroids. The family's history, viewed in relation to the evolution of their ligands, suggests that SRs evolved according to a principle of minimal specificity: at each point in time, receptors evolved ligand recognition criteria that were just specific enough to parse the set of endogenous substances to which they were exposed. By studying the atomic structures of resurrected SR proteins, we found that their promiscuity evolved because the ancestral binding cavity was larger than the primary ligand and contained excess hydrogen bonding capacity, allowing adventitious recognition of larger molecules with additional functional groups. Our findings provide an historical explanation for the sensitivity of modern SRs to natural and synthetic ligands—including endocrine-disrupting drugs and pollutants—and show that knowledge of history can contribute to ligand prediction. They suggest that SR promiscuity may reflect the limited power of selection within real biological systems to discriminate between perfect and “good enough.”</p

Evolution of Minimal Specificity and Promiscuity in Steroid Hormone Receptors

<div><p>Most proteins are regulated by physical interactions with other molecules; some are highly specific, but others interact with many partners. Despite much speculation, we know little about how and why specificity/promiscuity evolves in natural proteins. It is widely assumed that specific proteins evolved from more promiscuous ancient forms and that most proteins' specificity has been tuned to an optimal state by selection. Here we use ancestral protein reconstruction to trace the evolutionary history of ligand recognition in the steroid hormone receptors (SRs), a family of hormone-regulated animal transcription factors. We resurrected the deepest ancestral proteins in the SR family and characterized the structure-activity relationships by which they distinguished among ligands. We found that that the most ancient split in SR evolution involved a discrete switch from an ancient receptor for aromatized estrogens—including xenobiotics—to a derived receptor that recognized non-aromatized progestagens and corticosteroids. The family's history, viewed in relation to the evolution of their ligands, suggests that SRs evolved according to a principle of minimal specificity: at each point in time, receptors evolved ligand recognition criteria that were just specific enough to parse the set of endogenous substances to which they were exposed. By studying the atomic structures of resurrected SR proteins, we found that their promiscuity evolved because the ancestral binding cavity was larger than the primary ligand and contained excess hydrogen bonding capacity, allowing adventitious recognition of larger molecules with additional functional groups. Our findings provide an historical explanation for the sensitivity of modern SRs to natural and synthetic ligands—including endocrine-disrupting drugs and pollutants—and show that knowledge of history can contribute to ligand prediction. They suggest that SR promiscuity may reflect the limited power of selection within real biological systems to discriminate between perfect and “good enough.”</p> </div

Ligand-recognition rules of AncSR1 and AncSR2.

<p>A, The sensitivity of AncSR1-LBD (top panel) and AncSR2-LBD (bottom panel) to various hormones (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003072#pgen.1003072.s017" target="_blank">Table S4</a>) was characterized in a triplicate luciferase reporter assay and is displayed as EC50, the concentration at which half-maximal reporter activation is achieved. Error bars, 95% confidence interval. Sets of hormones are grouped by color and are numerically labeled according to the list below. B, AncSR1's ligand recognition criteria. Each pair of bars shows the EC50 of AncSR1 to a pair of hormones that differ only by aromatization of the A-ring (shown in red on the ligand structure and in the key). Unlike aromatization, substitution of a 17-keto or acetyl for estradiol's hydroxyl has only a weak effect on sensitivity, as shown by the small differences among pairs. C-I, AncSR2's ligand recognition criteria. Each pair of bars shows the sensitivity of the receptor to hormones that differ only in the functional group at specified positions or aromatization of the A-ring. Bar labels indicate the substance tested: 0, cholesterol, 1, 11-deoxycorticosterone, 2, 11-deoxycortisol; 3, corticosterone; 4, cortisol; 5, aldosterone; 6, progesterone; 7, 17α-hydroxyprogesterone; 8, 19-norprogesterone; 9, 4-pregnenolone; 10, 5-pregnenolone; 11, 20α hydroxyprogesterone; 12, 20β hydroxyprogesterone; 13, testosterone; 14, dihydrotestosterone; 15, 4-androstenediol; 16, 5-androstenediol; 17, 19-nortestosterone; 18, bolandiol; 19, estradiol; 20, estrone; 21, estriol; 22, 4-androstenedione; 23, 19-nor-1, 3, 5(10)-pregnatriene-3-ol-20-one (NPT).</p