A functional tacrolimus-releasing nerve wrap for enhancing nerve regeneration following surgical nerve repair.

JOURNAL/nrgr/04.03/01300535-202501000-00036/figure1/v/2024-05-14T021156Z/r/image-tiff Axonal regeneration following surgical nerve repair is slow and often incomplete, resulting in poor functional recovery which sometimes contributes to lifelong disability. Currently, there are no FDA-approved therapies available to promote nerve regeneration. Tacrolimus accelerates axonal regeneration, but systemic side effects presently outweigh its potential benefits for peripheral nerve surgery. The authors describe herein a biodegradable polyurethane-based drug delivery system for the sustained local release of tacrolimus at the nerve repair site, with suitable properties for scalable production and clinical application, aiming to promote nerve regeneration and functional recovery with minimal systemic drug exposure. Tacrolimus is encapsulated into co-axially electrospun polycarbonate-urethane nanofibers to generate an implantable nerve wrap that releases therapeutic doses of bioactive tacrolimus over 31 days. Size and drug loading are adjustable for applications in small and large caliber nerves, and the wrap degrades within 120 days into biocompatible byproducts. Tacrolimus released from the nerve wrap promotes axon elongation in vitro and accelerates nerve regeneration and functional recovery in preclinical nerve repair models while off-target systemic drug exposure is reduced by 80% compared with systemic delivery. Given its surgical suitability and preclinical efficacy and safety, this system may provide a readily translatable approach to support axonal regeneration and recovery in patients undergoing nerve surgery.

Genetic Encoding of a Photocaged Histidine for Light-Control of Protein Activity.

The use of light to control protein function is a critical tool in chemical biology. Here we describe the addition of a photocaged histidine to the genetic code. This unnatural amino acid becomes histidine upon exposure to light and allows for the optical control of enzymes that utilize active-site histidine residues. We demonstrate light-induced activation of a blue fluorescent protein and a chloramphenicol transferase. Further, we genetically encoded photocaged histidine in mammalian cells. We then used this approach in live cells for optical control of firefly luciferase and, Renilla luciferase. This tool should have utility in manipulating and controlling a wide range of biological processes.

Linkage-Specific Synthesis of Di-ubiquitin Probes Enabled by the Incorporation of Unnatural Amino Acid ThzK.

Di-ubiquitin (diUB) conjugates of defined linkages are useful tools for probing the functions of UB ligases, UB-binding proteins and deubiquitinating enzymes (DUBs) in coding, decoding and editing the signals carried by the UB chains. Here we developed an efficient method for linkage-specific synthesis of diUB probes based on the incorporation of the unnatural amino acid (UAA) Nϵ -L-thiaprolyl-L-Lys (L-ThzK) into UB for ligation with another UB at a defined Lys position. The diUB formed by the UAA-mediated ligation reaction has a G76C mutation on the side of donor UB for conjugation with E2 and E3 enzymes or undergoing dethiolation to generate a covalent trap for DUBs. The development of UAA mutagenesis for diUB synthesis provides an easy route for preparing linkage-specific UB-based probes to decipher the biological signals mediated by protein ubiquitination.

Phosphorylation independent eIF4E translational reprogramming of selective mRNAs determines tamoxifen resistance in breast cancer.

Eukaryotic translation initiation factor 4E (eIF4E) selectively promotes translation of mRNAs with atypically long and structured 5'-UTRs and has been implicated in drug resistance. Through genome-wide transcriptome and translatome analysis we revealed eIF4E overexpression could promote cellular activities mediated by ERα and FOXM1 signalling pathways. Whilst eIF4E overexpression could enhance the translation of both ERα and FOXM1, it also led to enhanced transcription of FOXM1. Polysome fractionation experiments confirmed eIF4E could modulate the translation of ERα and FOXM1 mRNA. The enhancement of FOXM1 transcription was contingent upon the presence of ERα, and it was the high levels of FOXM1 that conferred Tamoxifen resistance. Furthermore, tamoxifen resistance was conferred by phosphorylation independent eIF4E overexpression. Immunohistochemistry on 134 estrogen receptor (ER+) primary breast cancer samples confirmed that high eIF4E expression was significantly associated with increased ERα and FOXM1, and significantly associated with tamoxifen resistance. Our study uncovers a novel mechanism whereby phosphorylation independent eIF4E translational reprogramming in governing the protein synthesis of ERα and FOXM1 contributes to anti-estrogen insensitivity in ER+ breast cancer. In eIF4E overexpressing breast cancer, the increased ERα protein expression in turn enhances FOXM1 transcription, which together with its increased translation regulated by eIF4E, contributes to tamoxifen resistance. Coupled with eIF4E translational regulation, our study highlights an important mechanism conferring tamoxifen resistance via both ERα dependent and independent pathways.

Enhancing the incorporation of lysine derivatives into proteins with methylester forms of unnatural amino acids.

We have improved the incorporation of l- and d-forms of unnatural amino acid (UAA) Nε-thiaprolyl-l-lysine (ThzK) into ubiquitin (UB) and green fluorescent protein (GFP) by 2-6 folds with the use of the methylester forms of the UAAs in E coli cell culture. We also improved the yields of UAA-incorporated UB and GFP with the methylester forms of Nε-Boc-l-Lysine (BocK) and Nε-propargyl-l-Lysine (PrK) by 2-5 folds compared to their free acid forms. Our work demonstrated that using methylester-capped UAAs for protein expression is a useful strategy to enhance the yields of UAA-incorporated proteins.

Conformational Effect on the Large Amplitude Motions of 3,4-Dimethylanisole Explored by Microwave Spectroscopy.

The microwave spectrum of 3,4-dimethylanisole, a molecule containing three methyl groups allowing for internal rotation, was recorded using a pulsed molecular jet Fourier transform microwave spectrometer operating in the frequency range from 2.0 to 26.5 GHz. Quantum chemical calculations yielded two conformers with an  anti and a syn configuration of the methoxy group, both of which were assigned in the experimental spectrum. Torsional splittings due to the internal rotations of two methyl groups attached to the aromatic ring were resolved and analyzed. The rotational-torsional transitions could be reproduced to measurement accuracy, yielding well-determined rotational and internal rotation parameters. The torsional barriers of the methyl groups at the meta and para position were deduced to be 430.00(37) and 467.90(17) cm-1, respectively, for the syn-conformer. The respective values for the anti-conformer are 499.64(26) and 533.54(22) cm-1. A labeling scheme for the G18 group written as the semidirect product ( C3 I ⊗ C3 I) (× C s was introduced.

Polyphyllin D induces mitochondrial fragmentation and acts directly on the mitochondria to induce apoptosis in drug-resistant HepG2 cells.

We previously showed that polyphyllin D (PD) produced a stronger apoptotic effect in R-HepG2 with multi-drug resistance (MDR) than that in its parent HepG2 cells without MDR. In this study, PD was found to elicit mitochondrial fragmentation in live cells by using total internal reflection fluorescence microscopy (TIRFM). When mitochondria were isolated and treated directly with PD, a stronger swelling, deeper transmembrane depolarization, and more apoptosis-inducing factor (AIF) release were observed from the mitochondria of R-HepG2 than that of HepG2. These observations suggest that PD is a potent anti-cancer agent that bypasses MDR and elicits apoptosis via mitochondrial injury.

Polyphyllin D is a potent apoptosis inducer in drug-resistant HepG2 cells.

In a search for new anticancer agents, we identified a novel compound polyphyllin D (PD) (diosgenyl alpha-L-rhamnopyranosyl-(1-->2)-(alpha-L-arabinofuranosyl)-(1-->4)]-[beta-D-glucopyranoside) that induced DNA fragmentation and phosphatidyl-serine (PS) externalization in a hepatocellular carcinoma cell line HepG2 derivative with drug resistance (R-HepG2). PD is a saponin originally found in a tradition Chinese medicinal herb Paris polyphylla. It has been used to treat liver cancer in China for many years. We evaluated the cell-killing mechanisms of this compound in R-HepG2 and its parental cells. The mitochondrial apoptotic pathway was found to be involved in the PD-induced apoptosis because PD elicited depolarization of mitochondrial transmembrane potential (DeltaPsim), generation of H2O2, as well as release of cytochrome c and apoptosis-inducing factor in a dose- and time-dependent manner. In conclusion, we show for the first time that PD is a potent anticancer agent that can overcome drug resistance in R-HepG2 cells and elicit programmed cell death via mitochondrial dysfunction.

The decision process of leaving nursing.

This article reports the findings of a research study investigating the decision process of former division one nurses in deciding to leave the profession. Semi-structured interviews were conducted with 29 participants. For many participants, leaving nursing was not an easy decision. This article outlines the decision processes of five of the study participants to illustrate the complex psychological process associated with quitting. The insight gained may shed light on how to entice back nurses who have left the profession and address the needs of those thinking of leaving.

Caring as worrying: the experience of spousal carers.

BACKGROUND: With the emerging focus on home-based care, there is an increasing demand on spouses to look after their chronically ill partners at home. The theoretical aspects of caring have been much discussed in the literature, but the pragmatic aspects have received less attention. Carer stress has been explored, but little has been written about the meaning of caring to informal carers. AIM: The aim of this paper is to report one of the major themes that emerged from a study conducted between 1998 and 1999 to explicate the meaning of caring from the perspective of spousal carers for people with multiple sclerosis in order to shed light on and understand the challenges and demands these carers encountered. METHODOLOGY: An interpretive phenomenological approach was used to describe spousal carers' experiences of caring for their partner. Ten spousal carers of people with multiple sclerosis participated. Data were collected through unstructured in-depth interviews and analysed by the method of hermeneutic analysis. FINDINGS: This paper presents one of the major themes identified: 'caring as worrying'. While the meaning of caring that emerged from this theme supports many of the philosophical understandings of caring as discussed in the literature, worrying as a care responsibility provides a further insight. Caring as worrying describes caring as a complex emotional relationship of responsibility in these participants. They worried about their partners, their relationships with their partners and their future. They also worried about their own health, institutional care, and lack of government support. CONCLUSION: Spousal carers' worries have significant implications for health care professionals. The findings provide insight into the concerns and worries the carers of people with multiple sclerosis face when caring for their chronically ill partners at home.

The experience of spousal carers of people with multiple sclerosis.

This phenomenological-interpretative inquiry explores spousal carers' experience of caring for their partner while confronting many apparent losses. Ten spousal carers of people with multiple sclerosis (MS) participated in the study. The authors collected data using unstructured in-depth interviews and analyzed them using a hermeneutic method. The constitutive pattern, Weaving Through a Web of Paradoxes, that emerged from the data described how these participants' experience in caring for their partner has changed their way of living and their being. The authors present in this article some of the paradoxes that capture carers' experiences of loss and gain, and their feelings of vulnerability and strength. The insight gained from this study adds new understanding of responses to non-death-related losses.