Unveiling nurses' end-of-life care experiences: Moral distress and impacts.

BACKGROUND: Nurses providing care to patients with end-of-life or terminal illnesses often encounter ethically challenging situations leading to moral distress. However, existing quantitative studies have examined moral distress using instruments that address general clinical situations rather than those specific to end-of-life care. Furthermore, qualitative studies have often been limited to participants from a single unit or those experiencing moral distress-induced circumstances. A comprehensive and integrated understanding of the overarching process of moral distress is vital to discern the unique circumstances surrounding end-of-life care and its consequential impacts. RESEARCH OBJECTIVES: To explore the moral distress experiences of nurses who are frequently involved in caring for patients with end-of-life or terminal illnesses and apply it to two existing theories: the model of moral distress and the ecological model. RESEARCH DESIGN: A qualitative descriptive approach was employed. PARTICIPANTS AND RESEARCH CONTEXT: Seven focus group interviews involving 30 nurses were performed. The subsequent transcriptions underwent rigorous content analysis. ETHICAL CONSIDERATIONS: We obtained Institutional Review Board approval from a university. Focus group interviews were conducted with nurses who agreed to participate and signed the consent form. FINDINGS: The moral distress-inducing factors and nurses' perceived impact of moral distress were identified and categorized based on moral distress theories and ecological models. A total of 15 categories and 30 subcategories across the following 4 domains were derived: (1) intrapersonal, (2) interpersonal, (3) organizational, and (4) structural factors. CONCLUSIONS: End-of-life-specific circumstances induced moral distress among nurses, with both negative and positive impacts identified. Effective organizational and policy support is essential to manage conflicts, form a healthy organizational culture, provide training, and prevent unnecessary expenses due to the negative consequences of moral distress.

Spiritual Care Guide in Hospice∙Palliative Care.

The Spiritual Care Guide in Hospice∙Palliative Care is evidence-based and focuses on the universal and integral aspects of human spirituality-such as meaning and purpose, interconnectedness, and transcendence-which go beyond any specific religion. This guide was crafted to improve the spiritual well-being of adult patients aged 19 and older, as well as their families, who are receiving end-of-life care. The provision of spiritual care in hospice and palliative settings aims to assist patients and their families in finding life's meaning and purpose, restoring love and relationships, and helping them come to terms with death while maintaining hope. It is recommended that spiritual needs and the interventions provided are periodically reassessed and evaluated, with the findings recorded. Additionally, hospice and palliative care teams are encouraged to pursue ongoing education and training in spiritual care. Although challenges exist in universally applying this guide across all hospice and palliative care organizations in Korea-due to varying resources and the specific environments of medical institutions-it is significant that the Korean Society for Hospice and Palliative Care has introduced a spiritual care guide poised to enhance the spiritual well-being and quality of care for hospice and palliative care patients.

Effects of a Meaning-Centered Spiritual Care Training Program for Hospice Palliative Care Teams in South Korea: A Nonrandomized Controlled Trial.

BACKGROUND: Spiritual care is an essential part and a core component of quality palliative care, as identified by the World Health Organization. However, spiritual care training for hospice palliative care teams (HPCTs) is infrequent. OBJECTIVE: The aim of this study was to investigate the effects of a meaning-centered spiritual care training program for HPCTs (McSCTP-HPCT). METHODS: This study used a nonrandomized controlled design. The McSCTP-HPCT comprised 5 modules. The participants were HPCTs working in 15 national hospice institutions and were allocated to either the experimental group (n = 33) or the control group (n = 27) based on the participating institutions' preference. Three outcome variables were tested: spiritual care competency, spiritual care therapeutics, and compassion fatigue. Data were analyzed using descriptive statistics, χ 2 test, 1-way analysis of variance, and repeated-measures analysis of variance. RESULTS: There was a significant difference in the interaction between measurement time and group assignment in spiritual care competency ( P = .002) and spiritual care therapeutics ( P = .038), whereas no significant difference was found for compassion fatigue ( P = .716). CONCLUSION: The McSCTP-HPCT conducted in this study shows effectiveness in increasing the spiritual care competency and spiritual care therapeutics of HPCTs and may support the importance of spiritual care training. IMPLICATIONS FOR PRACTICE: The McSCTP-HPCTs adds to the scientific evidence on spiritual care and has the capacity to improve the quality of care for patients with a life-threatening illness.

Deoxyhypusine synthase mutations alter the post-translational modification of eukaryotic initiation factor 5A resulting in impaired human and mouse neural homeostasis.

DHPS deficiency is a rare genetic disease caused by biallelic hypomorphic variants in the Deoxyhypusine synthase (DHPS) gene. The DHPS enzyme functions in mRNA translation by catalyzing the post-translational modification, and therefore activation, of eukaryotic initiation factor 5A (eIF5A). The observed clinical outcomes associated with human mutations in DHPS include developmental delay, intellectual disability, and seizures. Therefore, to increase our understanding of this rare disease, it is critical to determine the mechanisms by which mutations in DHPS alter neurodevelopment. In this study, we have generated patient-derived lymphoblast cell lines and demonstrated that human DHPS variants alter DHPS protein abundance and impair enzyme function. Moreover, we observe a shift in the abundance of the post-translationally modified forms of eIF5A; specifically, an increase in the nuclear localized acetylated form (eIF5AAcK47) and concomitant decrease in the cytoplasmic localized hypusinated form (eIF5AHYP). Generation and characterization of a mouse model with a genetic deletion of Dhps in the brain at birth shows that loss of hypusine biosynthesis impacts neuronal function due to impaired eIF5AHYP-dependent mRNA translation; this translation defect results in altered expression of proteins required for proper neuronal development and function. This study reveals new insight into the biological consequences and molecular impact of human DHPS deficiency and provides valuable information toward the goal of developing treatment strategies for this rare disease.

Bi-allelic variants in DOHH, catalyzing the last step of hypusine biosynthesis, are associated with a neurodevelopmental disorder.

Deoxyhypusine hydroxylase (DOHH) is the enzyme catalyzing the second step in the post-translational synthesis of hypusine [Nε-(4-amino-2-hydroxybutyl)lysine] in the eukaryotic initiation factor 5A (eIF5A). Hypusine is formed exclusively in eIF5A by two sequential enzymatic steps catalyzed by deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase (DOHH). Hypusinated eIF5A is essential for translation and cell proliferation in eukaryotes, and all three genes encoding eIF5A, DHPS, and DOHH are highly conserved throughout eukaryotes. Pathogenic variants affecting either DHPS or EIF5A have been previously associated with neurodevelopmental disorders. Using trio exome sequencing, we identified rare bi-allelic pathogenic missense and truncating DOHH variants segregating with disease in five affected individuals from four unrelated families. The DOHH variants are associated with a neurodevelopmental phenotype that is similar to phenotypes caused by DHPS or EIF5A variants and includes global developmental delay, intellectual disability, facial dysmorphism, and microcephaly. A two-dimensional gel analyses revealed the accumulation of deoxyhypusine-containing eIF5A [eIF5A(Dhp)] and a reduction in the hypusinated eIF5A in fibroblasts derived from affected individuals, providing biochemical evidence for deficiency of DOHH activity in cells carrying the bi-allelic DOHH variants. Our data suggest that rare bi-allelic variants in DOHH result in reduced enzyme activity, limit the hypusination of eIF5A, and thereby lead to a neurodevelopmental disorder.

Nurses' Perceived Needs and Barriers Regarding Pediatric Palliative Care: A Mixed-Methods Study.

Purpose: This study aimed to describe nurses' perceived needs and barriers to pediatric palliative care (PPC). Methods: Mixed methods with an embedded design were applied. An online survey was conducted for nurses who participated in the End-of-Life Nursing Education Consortium- Pediatric Palliative Care (ELNEC-PPC) train-the-trainer program, of whom 63 responded. Quantitative data were collected with a survey questionnaire developed through the Delphi method. The 47 items for needs and 15 items for barriers to PPC were analyzed with descriptive statistics. Qualitative data were collected through open- ended questions and analyzed with topic modeling techniques. Results: The mean scores of most subdomains of the PPC needs were 3.5 or higher out of 4, and those of PPC barriers ranged from 3.22 to 3.56, indicating the items in the questionnaire developed in this study properly reflect each factor. The needs for PPC were divided into 4 categories "children and adolescents," "families," "PPC management system," and "community-based PPC." Meanwhile, PPC barriers were divided into 3 categories "healthcare delivery system," "healthcare provider," and "client." The keywords derived from the topic modeling were perception, palliative, children, and education for necessities and lack, perception, medical care, professional care providers, service, and system for barriers to PPC. Conclusion: In this study, by using mixed-methods, items of nurses' perceived needs and barriers to PPC were identified, categorized, and weighted, and their meanings were explored. For the stable establishment of PPC, the priority should be given to improving perceptions of PPC, establishing an appropriate system, and training professional care providers.

Post-translational formation of hypusine in eIF5A: implications in human neurodevelopment.

Hypusine [Nε-(4-amino-2-hydroxybutyl)lysine] is a derivative of lysine that is formed post-translationally in the eukaryotic initiation factor 5A (eIF5A). Its occurrence at a single site in one cellular protein defines hypusine synthesis as one of the most specific post-translational modifications. Synthesis of hypusine involves two enzymatic steps: first, deoxyhypusine synthase (DHPS) cleaves the 4-aminobutyl moiety of spermidine and transfers it to the ε-amino group of a specific lysine residue of the eIF5A precursor protein to form an intermediate, deoxyhypusine [Nε-(4-aminobutyl)lysine]. This intermediate is subsequently hydroxylated by deoxyhypusine hydroxylase (DOHH) to form hypusine in eIF5A. eIF5A, DHPS, and DOHH are highly conserved in all eukaryotes, and both enzymes exhibit a strict specificity toward eIF5A substrates. eIF5A promotes translation elongation globally by alleviating ribosome stalling and it also facilitates translation termination. Hypusine is required for the activity of eIF5A, mammalian cell proliferation, and animal development. Homozygous knockout of any of the three genes, Eif5a, Dhps, or Dohh, leads to embryonic lethality in mice. eIF5A has been implicated in various human pathological conditions. A recent genetic study reveals that heterozygous germline EIF5A variants cause Faundes-Banka syndrome, a craniofacial-neurodevelopmental malformations in humans. Biallelic variants of DHPS were identified as the genetic basis underlying a rare inherited neurodevelopmental disorder. Furthermore, biallelic DOHH variants also appear to be associated with neurodevelopmental disorder. The clinical phenotypes of these patients include intellectual disability, developmental delay, seizures, microcephaly, growth impairment, and/or facial dysmorphisms. Taken together, these findings underscore the importance of eIF5A and the hypusine modification pathway in neurodevelopment in humans.

Neuron-specific ablation of eIF5A or deoxyhypusine synthase leads to impairments in growth, viability, neurodevelopment, and cognitive functions in mice.

Eukaryotic initiation factor 5A (eIF5A)†,‡ is an essential protein that requires a unique amino acid, hypusine, for its activity. Hypusine is formed exclusively in eIF5A post-translationally via two enzymes, deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase. Each of the genes encoding these proteins, Eif5a, Dhps, and Dohh, is required for mouse embryonic development. Variants in EIF5A or DHPS were recently identified as the genetic basis underlying certain rare neurodevelopmental disorders in humans. To investigate the roles of eIF5A and DHPS in brain development, we generated four conditional KO mouse strains using the Emx1-Cre or Camk2a-Cre strains and examined the effects of temporal- and region-specific deletion of Eif5a or Dhps. The conditional deletion of Dhps or Eif5a by Emx1 promotor-driven Cre expression (E9.5, in the cortex and hippocampus) led to gross defects in forebrain development, reduced growth, and premature death. On the other hand, the conditional deletion of Dhps or Eif5a by Camk2a promoter-driven Cre expression (postnatal, mainly in the CA1 region of the hippocampus) did not lead to global developmental defects; rather, these KO animals exhibited severe impairment in spatial learning, contextual learning, and memory when subjected to the Morris water maze and a contextual learning test. In both models, the Dhps-KO mice displayed more severe impairment than their Eif5a-KO counterparts. The observed defects in the brain, global development, or cognitive functions most likely result from translation errors due to a deficiency in active, hypusinated eIF5A. Our study underscores the important roles of eIF5A and DHPS in neurodevelopment.

A meaning-centered spiritual care training program for hospice palliative care teams in South Korea: development and preliminary evaluation.

BACKGROUND: Spirituality is a fundamental, intrinsic aspect of human beings and should be a core component of quality palliative care. There is an urgent need to train hospice palliative care teams (HPCTs) to enhance their ability to provide spiritual care. This study aimed to develop and evaluate a meaning-centered, spiritual care training program (McSCTP) for HPCTs (McSCTP-HPCTs). METHODS: The modules' content was informed by Viktor Frankl's meaning-centered logotherapy with its emphasis on spiritual resources, as well as the spiritual care model of the Interprofessional Spiritual Care Education Curriculum (ISPEC). Following development, we conducted a pilot test with four nurses. We used the results to inform the final program, which we tested in an intervention involving 13 members of HPCTs. We took measurements using self-administered questionnaires at three points before and after the intervention. Using descriptive statistics, the Mann-Whitney U test, and the Kruskal-Wallis test, we analyzed the participants' demographic and career-related characteristics, as well as the degree of variance between three outcome variables: compassion fatigue (CF), spiritual care competencies (SCCs), and spiritual care therapeutics (SCT). RESULTS: We divided the McSCTP-HPCTs into five modules. Module I: The HPCTs' SCC evaluation, understanding the major concepts of spiritual care and logotherapy; Modules II-IV: Meaning-centered interventions (MCIs) related to spiritual needs (existential, relational, and transcendental/religious); Module V: The process of meaning-centered spiritual care. The preliminary evaluation revealed significant differences in all three outcome variables at the posttest point (CF, p = 0.037; SCCs, p = 0.005; SCT, p = 0.002). At the four-week follow-up test point, we only found statistical significance with the SCCs (p = 0.006). CONCLUSIONS: The McSCTP-HPCTs is suitable for use in clinical settings and provides evidence for assessing the SCCs of HPCTs.

Education, Role, and Prospects of Advanced Practice Nurses in Hospice and Palliative Care in South Korea.

Hospice palliative care refers to holistic care provided by an interdisciplinary team aimed at improving the quality of life of patients suffering from life-threatening diseases and their families. Among interdisciplinary team members, hospice advanced practice nurses (APNs) trained as master's-level advanced nursing professionals are leaders who play an important role in providing patient-centered care and improving the quality of services. The Medical Service Act revised in 2018 requires the scope of practice of APNs in each field to be specified in the Ordinance of the Ministry of Health and Welfare. Accordingly, discussions on the role and scope of practice of hospice APNs are actively underway. In this review, the curriculum of hospice APNs, their work responsibilities and roles, and their current status are reviewed, and the future direction of the hospice APN system is also discussed.

Delirium-Related Knowledge, Caregiving Performance, Stress Levels, and Mental Health of Family Caregivers of Terminal Cancer Patients with Delirium in a Hospice Care Unit.

Purpose: The purpose of this study was to examine the knowledge, caregiving performance, stress levels, and mental health of family caregivers of terminal cancer patients with delirium, insofar as these characteristics are relevant for delirium. Methods: Between May 1, 2019, and June 1, 2020, 96 family caregivers of terminal cancer patients with delirium completed a structured survey, the results of which were analyzed. Results: The average correct answer rate for delirium-related knowledge was 53.2% across all subcategories, which included knowledge of causes (41.5%), symptoms (65.4%), and caregiving (51.7%). The average score for family caregivers' performance of caregiving for delirium was 2.60±0.5, with subcategories including caregiving for patients without delirium (2.16±0.95), caregiving for patients with delirium (2.84±1.01), and stress related to caregiving for delirium (39.88±16.55), as well as categories such as patient-related caregiving (44.32±28.98), duty-related caregiving (44.21±30.15), and interpersonal relationship-related caregiving (22.35±25.03). For mental health, the average score among family caregivers was 1.96±0.70, with the highest score being for the category of additional items (2.28±0.84). Family caregivers of patients with hyperactive delirium as the delirium subtype had higher scores for caregiving performance than caregivers of patients with mixed delirium. Conclusion: Scores for the delirium-related knowledge and caregiving performance of family caregivers were low, while their caregiving stress levels were high due to their lack of knowledge and experience. This indicates the importance of delirium-related education for family members of patients with delirium and the necessity of developing nursing intervention programs to help manage stress and promote mental health among family caregivers.

Heart Failure Statistics in Korea, 2020: A Report from the Korean Society of Heart Failure.

Background and Objectives: Heart failure (HF) is a disease with high morbidity and mortality. With ageing society and increasing prevalence of risk factors of HF, the prevalence of HF is expected to increase, as well. In this official report of the Korean Society of Heart Failure the epidemiology of HF in Korea is presented. Methods: The data of Korean National Health Insurance big data, the Korean Heart Failure (KorHF) and the Korean Acute Heart Failure (KorAHF) registries have been used. Results: In 2018, the prevalence, incidence, mortality of HF patients, and mortality due to HF were 2,261, 579, 245, and 10.4 per 100.000 persons, respectively. Regarding the temporal trend, there was a continuous increase in HF prevalence (0.77% in 2002, 1.48% in 2013, and 2.24% in 2018) and HF related deaths. The most common etiology for HF was ischemic origin, and the dominant subtype was HF with reduced ejection fraction (EF), defined as EF ≤40%. Of these, 77.6%, 58.0%, and 55.1% received renin-angiotensin-system inhibitors (angiotensin-converting-enzyme inhibitors or angiotensin-receptor-blockers), beta-blockers, and aldosterone-antagonists, respectively. In 2018, 1,542 implantable cardiac defibrillators and 272 cardiac resynchronization therapy devices were implanted, and 176 patients received heart transplantation. With improvement of pharmacologic and non-pharmacological therapy, the survival time of HF has been improving in the last 2 decades; nonetheless, it is associated with enormous increase in medical costs. Conclusions: The prevalence of HF has been increasing in Korea. With improvement of therapy, the prognosis of HF has been improving, too. Nonetheless, appropriate interventions are necessary to prevent HF.

Clinical Practice Guideline for Care in the Last Days of Life.

A clinical practice guideline for patients in the dying process in general wards and their families, developed through an evidence-based process, is presented herein. The purpose of this guideline is to enable a peaceful death based on an understanding of suitable management of patients' physical and mental symptoms, psychological support, appropriate decision-making, family care, and clearly-defined team roles. Although there are limits to the available evidence regarding medical issues in patients facing death, the final recommendations were determined from expert advice and feedback, considering values and preferences related to medical treatment, benefits and harms, and applicability in the real world. This guideline should be applied in a way that takes into account specific health care environments, including the resources of medical staff and differences in the available resources of each institution. This guideline can be used by all medical institutions in South Korea.

Elevation of cellular Mg2+ levels by the Mg2+ transporter, Alr1, supports growth of polyamine-deficient Saccharomyces cerevisiae cells.

The polyamines putrescine, spermidine, and spermine are required for normal eukaryotic cellular functions. However, the minimum requirement for polyamines varies widely, ranging from very high concentrations (mm) in mammalian cells to extremely low in the yeast Saccharomyces cerevisiae Yeast strains deficient in polyamine biosynthesis (spe1Δ, lacking ornithine decarboxylase, and spe2Δ, lacking SAM decarboxylase) require externally supplied polyamines, but supplementation with as little as 10-8 m spermidine restores their growth. Here, we report that culturing a spe1Δ mutant or a spe2Δ mutant in a standard polyamine-free minimal medium (SDC) leads to marked increases in cellular Mg2+ content. To determine which yeast Mg2+ transporter mediated this increase, we generated mutant strains with a deletion of SPE1 or SPE2 combined with a deletion of one of the three Mg2+ transporter genes, ALR1, ALR2, and MNR2, known to maintain cytosolic Mg2+ concentration. Neither Alr2 nor Mnr2 was required for increased Mg2+ accumulation, as all four double mutants (spe1Δ alr2Δ, spe2Δ alr2Δ, spe1Δ mnr2Δ, and spe2Δ mnr2Δ) exhibited significant Mg2+ accumulation upon polyamine depletion. In contrast, a spe2Δ alr1Δ double mutant cultured in SDC exhibited little increase in Mg2+ content and displayed severe growth defects compared with single mutants alr1Δ and spe2Δ under polyamine-deficient conditions. These findings indicate that Alr1 is required for the up-regulation of the Mg2+ content in polyamine-depleted cells and suggest that elevated Mg2+ can support growth of polyamine-deficient S. cerevisiae mutants. Up-regulation of cellular polyamine content in a Mg2+-deficient alr1Δ mutant provided further evidence for a cross-talk between Mg2+ and polyamine metabolism.

Recessive Rare Variants in Deoxyhypusine Synthase, an Enzyme Involved in the Synthesis of Hypusine, Are Associated with a Neurodevelopmental Disorder.

Hypusine is formed post-translationally from lysine and is found in a single cellular protein, eukaryotic translation initiation factor-5A (eIF5A), and its homolog eIF5A2. Biosynthesis of hypusine is a two-step reaction involving the enzymes deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase (DOHH). eIF5A is highly conserved throughout eukaryotic evolution and plays a role in mRNA translation, cellular proliferation, cellular differentiation, and inflammation. DHPS is also highly conserved and is essential for life, as Dhps-null mice are embryonic lethal. Using exome sequencing, we identified rare biallelic, recurrent, predicted likely pathogenic variants in DHPS segregating with disease in five affected individuals from four unrelated families. These individuals have similar neurodevelopmental features that include global developmental delay and seizures. Two of four affected females have short stature. All five affected individuals share a recurrent missense variant (c.518A>G [p.Asn173Ser]) in trans with a likely gene disrupting variant (c.1014+1G>A, c.912_917delTTACAT [p.Tyr305_Ile306del], or c.1A>G [p.Met1?]). cDNA studies demonstrated that the c.1014+1G>A variant causes aberrant splicing. Recombinant DHPS enzyme harboring either the p.Asn173Ser or p.Tyr305_Ile306del variant showed reduced (20%) or absent in vitro activity, respectively. We co-transfected constructs overexpressing HA-tagged DHPS (wild-type or mutant) and GFP-tagged eIF5A into HEK293T cells to determine the effect of these variants on hypusine biosynthesis and observed that the p.Tyr305_Ile306del and p.Asn173Ser variants resulted in reduced hypusination of eIF5A compared to wild-type DHPS enzyme. Our data suggest that rare biallelic variants in DHPS result in reduced enzyme activity that limits the hypusination of eIF5A and are associated with a neurodevelopmental disorder.

Hypusine, a polyamine-derived amino acid critical for eukaryotic translation.

The natural amino acid hypusine (Nϵ-4-amino-2-hydroxybutyl(lysine)) is derived from the polyamine spermidine, and occurs only in a single family of cellular proteins, eukaryotic translation factor 5A (eIF5A) isoforms. Hypusine is formed by conjugation of the aminobutyl moiety of spermidine to a specific lysine residue of this protein. The posttranslational synthesis of hypusine involves two enzymatic steps, catalyzed by deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase (DOHH). Hypusine is essential for eIF5A activity. Inactivation of either the eIF5A or the DHPS gene is lethal in yeast and mouse, underscoring the vital role of eIF5A hypusination in eukaryotic cell growth and animal development. The long and basic side chain of the hypusine residue promotes eIF5A-mediated translation elongation by facilitating peptide bond formation at polyproline stretches and at many other ribosome-pausing sites. It also enhances translation termination by stimulating peptide release. By promoting translation, the hypusine modification of eIF5A provides a key link between polyamines and cell growth regulation. eIF5A has been implicated in several human pathological conditions. Recent genetic data suggest that eIF5A haploinsufficiency or impaired deoxyhypusine synthase activity is associated with neurodevelopmental disorders in humans.

Rewiring of cisplatin-resistant bladder cancer cells through epigenetic regulation of genes involved in amino acid metabolism.

Alterations in DNA methylation are important epigenetic markers in bladder cancer (BC). These epigenome modifications may drive the mechanisms of aggressive chemo-resistant BC. Clinicopathological biomarkers that indicate chemotherapeutic resistance are critical for better assessing treatment strategies for individual patients. Thus, in this study, we aimed to determine whether DNA methylation of certain metabolic enzymes is significantly altered in cisplatin-resistant BC cells. Methods: To characterize CpG methylation and nucleosome accessibility in cisplatin-resistant BC cells, the Illumina Infinium HM450 DNA methylation assay was performed. Perturbed gene expression was found to be associated with cisplatin resistance, and the biological roles of spermidine/spermine N1-acetyltransferase (SAT1) and argininosuccinate synthase 1 (ASS1) were further studied using qRT-PCR analysis and various cell biology assays, including western blot. Results:ASS1 and SAT1, genes for amino acid and polyamine metabolism catalysts, respectively, were found to be vastly hypermethylated, resulting in greatly downregulated expression. ASS1 expression is of particular interest because prior studies have demonstrated its potential association with BC stage and recurrence. In regard to chemoresistance, we found that aberrant expression or induced stimulation of SAT1 restored cisplatin sensitivity in the cell culture system. We also found that the addition of exogenous arginine deiminase through administration of ADI-PEG 20 (pegylated arginine deiminase) increased ASS1 expression and enhanced cisplatin's apoptotic effects. Conclusions: Our study demonstrates a novel mechanistic link between the epigenetic perturbation of SAT1 and ASS1 and cancer metabolism in cisplatin-resistant bladder cancer cells. These findings suggest potential utility of SAT1 and ASS1 as predictive biomarkers in re-sensitizing bladder cancer to chemotherapy and personalizing therapy.

A new non-radioactive deoxyhypusine synthase assay adaptable to high throughput screening.

Deoxyhypusine synthase (DHS) catalyzes the post-translational modification of eukaryotic translation factor 5A (eIF5A) by the polyamine, spermidine, that converts one specific lysine residue to deoxyhypusine [N ε -4-aminobutyl(lysine)], which is subsequently hydroxylated to hypusine [N ε -4-amino-2-hydroxybutyl(lysine)]. Hypusine synthesis represents the most critical function of polyamine. As eIF5A has been implicated in various human diseases, identification of specific inhibitors of hypusine modification is of vital importance. DHS catalyzes a complex reaction that occurs in two stages, first, the NAD-dependent cleavage of spermidine to form an enzyme-butylimine intermediate and enzyme-bound NADH, and second, the transfer of the butylimine moiety from the enzyme intermediate to the eIF5A precursor and subsequent reduction of the eIF5A-butylimine intermediate by enzyme-bound NADH to form deoxyhypusine [N ε -4-aminobutyl(lysine)]. Our data demonstrate that there is a measurable release of enzyme-bound NADH in the absence of eIF5A precursor and that the DHS activity can be determined by coupling the first phase reaction with the NADH-Glo assay in which the generation of luminescence is dependent on NADH derived from the DHS partial reaction. The conventional DHS assay that measures the incorporation of radioactivity from [1,8-3H]spermidine into the eIF5A precursor in the complete reaction cannot be readily adapted for high throughput screening (HTS). In contrast, the non-radioactive DHS/NADH-Glo coupled assay is highly specific, sensitive and reproducible and could be configured for HTS of small molecule libraries for the identification of new inhibitors of DHS. Furthermore, the coupled assay provides new insights into the dynamics of the DHS reaction especially regarding the fate of NADH.

X-ray absorption spectroscopic characterization of the diferric-peroxo intermediate of human deoxyhypusine hydroxylase in the presence of its substrate eIF5a.

Human deoxyhypusine hydroxylase (hDOHH) is an enzyme that is involved in the critical post-translational modification of the eukaryotic translation initiation factor 5A (eIF5A). Following the conversion of a lysine residue on eIF5A to deoxyhypusine (Dhp) by deoxyhypusine synthase, hDOHH hydroxylates Dhp to yield the unusual amino acid residue hypusine (Hpu), a modification that is essential for eIF5A to promote peptide synthesis at the ribosome, among other functions. Purification of hDOHH overexpressed in E. coli affords enzyme that is blue in color, a feature that has been associated with the presence of a peroxo-bridged diiron(III) active site. To gain further insight into the nature of the diiron site and how it may change as hDOHH goes through the catalytic cycle, we have conducted X-ray absorption spectroscopic studies of hDOHH on five samples that represent different species along its reaction pathway. Structural analysis of each species has been carried out, starting with the reduced diferrous state, proceeding through its O2 adduct, and ending with a diferric decay product. Our results show that the Fe⋯Fe distances found for the five samples fall within a narrow range of 3.4-3.5 Å, suggesting that hDOHH has a fairly constrained active site. This pattern differs significantly from what has been associated with canonical dioxygen activating nonheme diiron enzymes, such as soluble methane monooxygenase and Class 1A ribonucleotide reductases, for which the Fe⋯Fe distance can change by as much as 1 Å during the redox cycle. These results suggest that the O2 activation mechanism for hDOHH deviates somewhat from that associated with the canonical nonheme diiron enzymes, opening the door to new mechanistic possibilities for this intriguing family of enzymes.