Antiplatelet effects of the CEACAM1-derived peptide QDTT

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) restricts platelet activation via platelet collagen receptor GPVI/FcRγ-chain. In this study, screening against collagen-induced platelet aggregation was performed to identify functional CEACAM1 extracellular domain fragments. CEACAM1 fragments, including Ala-substituted peptides, were synthesized. Platelet assays were conducted on healthy donor samples for aggregation, cytotoxicity, adhesion, spreading, and secretion. Mice were used for tail bleeding and FeCl3-induced thrombosis experiments. Clot retraction was assessed using platelet-rich plasma. Extracellular segments of CEACAM1 and A1 domain-derived peptide QDTT were identified, while N, A2, and B domains showed no involvement. QDTT inhibited platelet aggregation. Ala substitution for essential amino acids (Asp139, Thr141, Tyr142, Trp144, and Trp145) in the QDTT sequence abrogated collagen-induced aggregation inhibition. QDTT also suppressed platelet secretion and "inside-out" GP IIb/IIIa activation by convulxin, along with inhibiting PI3K/Akt pathways. QDTT curtailed FeCl3-induced mesenteric thrombosis without significantly prolonging bleeding time, implying the potential of CEACAM1 A1 domain against platelet activation without raising bleeding risk, thus paving the way for novel antiplatelet drugs.

Molecular identification of Opisthorchis viverrini among the northeastern Cambodian population by internal transcribed spacer 2 based polymerase chain reaction

The southeast Asian fluke Opisthorchis viverrini remains endemic, particularly in Thailand, Lao PDR, Cambodia, Vietnam, and Myanmar. However, there is a lack of data on the prevalence of liver fluke infection in Kratie Province in northeastern Cambodia. The present study aimed to detect O. viverrini DNA in fecal specimens by using the internal transcribed spacer 2 (ITS2) region of ribosomal DNA (rDNA) based on polymerase chain reaction (PCR). The prevalence and percentage of O. viverrini infection were described by data analysis. Bivariate binary logistic regression analysis was used to look at the related prevalence of O. viverrini infection. A total of 6.89% from 377 fecal samples were found positive of O. viverrini DNA. The prevalence of O. viverrini infection was found to be higher in men (8.92%) than in women (5.45%), and to be associated more frequently with younger age groups (13.40%), illiteracy (8.74%), participation in other careers (non-specific occupations) (11.63%), and residence in the Trapaing Srae village (9.94%) of the Snuol district, Kratie Province. Age groups under 20 years old were significantly linked with O. viverrini infection, with ORadj=0.601, 95% CI=0.410-0.882, p=0.009 and significant value established at (P<0.05). This study demonstrates that O. viverrini infection is distributed in rural areas located near freshwater reservoirs. Therefore, active surveillance, clinical examination of association with hepatobiliary, cholangiocarcinoma, and health education are needed.

Luteolin inhibits GPVI-mediated platelet activation, oxidative stress, and thrombosis

Introduction: Luteolin inhibits platelet activation and thrombus formation, but the mechanisms are unclear. This study investigated the effects of luteolin on GPVI-mediated platelet activation in vitro and explored the effect of luteolin on thrombosis, coagulation, and platelet production in vivo. Methods: Washed human platelets were used for aggregation, membrane protein expression, ATP, Ca2+, and LDH release, platelet adhesion/spreading, and clot retraction experiments. Washed human platelets were used to detect collagen and convulxin-induced reactive oxygen species production and endogenous antioxidant effects. C57BL/6 male mice were used for ferric chloride-induced mesenteric thrombosis, collagen-epinephrine induced acute pulmonary embolism, tail bleeding, coagulation function, and luteolin toxicity experiments. The interaction between luteolin and GPVI was analyzed using solid phase binding assay and surface plasmon resonance (SPR). Results: Luteolin inhibited collagen- and convulxin-mediated platelet aggregation, adhesion, and release. Luteolin inhibited collagen- and convulxin-induced platelet ROS production and increased platelet endogenous antioxidant capacity. Luteolin reduced convulxin-induced activation of ITAM and MAPK signaling molecules. Molecular docking simulation showed that luteolin forms hydrogen bonds with GPVI. The solid phase binding assay showed that luteolin inhibited the interaction between collagen and GPVI. Surface plasmon resonance showed that luteolin bonded GPVI. Luteolin inhibited integrin αIIbβ3-mediated platelet activation. Luteolin inhibited mesenteric artery thrombosis and collagen- adrenergic-induced pulmonary thrombosis in mice. Luteolin decreased oxidative stress in vivo. Luteolin did not affect coagulation, hemostasis, or platelet production in mice. Discussion: Luteolin may be an effective and safe antiplatelet agent target for GPVI. A new mechanism (decreased oxidative stress) for the anti-platelet activity of luteolin has been identified.

Intestinal parasitic infections and risk factors among the population in Cambodia

Many species of helminths and protozoa caused intestinal parasitic infections (IPIs). It belongs to neglected tropical diseases (NTDs) and remains a major public health problem in several Southeast Asian countries. The present study aimed to investigate the prevalence of IPIs and associated risk factors among the population in Kratie Province in northeastern Cambodia and Phnom Penh is the capital that locates in southern Cambodia. Fecal specimens (n=366) were collected in 10 villages in Kratie Province and Phnom Penh from 2019 to 2021. They were processed using the formalin ethyl-acetate concentration technique (FECT) to investigate parasites at egg and cyst stages and then examined under a light microscope. The results revealed that the prevalence of IPIs among the population in Kratie Province (n=317) and Phnom Penh (n=49) was 16.12% (n=59); of Kratie Province (n=50, 13.66%) and Phnom Penh (n=9, 2.46%), 12.02% (n=44) were helminths and 4.10% (n=15) were protozoa. The parasitic infection rate was higher in males (9.02%) than in females (7.10%) and more likely to be due to helminths (7.38%) than protozoa (1.64%). Prevalence of Opisthorchis viverrini was the highest (5.74%), followed by those of Entamoeba coli (4.10%), hookworm (3.83%), Ascaris lumbricoides (1.10%), Hymenolepis nana (1.09%), Taenia spp. (0.54%), Trichuris trichiura (0.55%), and Enterobius vermicularis (0.27%), respectively. Moreover, O. viverrini infection was the most common infection in the <20-year age group in Kratie Province. In addition, the bivariate and multivariate analyses showed that the association between gender. Gender was a significant risk factor positively associated with O. viverrini and hookworm infections (OR_adj=0.318, 95% CI=0.122-0.8270, P=0.019 and OR_adj=0.085, 95% CI=0.017-0.436, P=0.003, respectively). In conclusion, the IPIs were highly prevalent, especially O. viverrini and hookworm infections, among the population in Cambodia. These IPIs impact the public health burden but can be prevented by education regarding good sanitary practices in this community.

Effect of Evodiamine on Collagen-Induced Platelet Activation and Thrombosis

Evodia rutaecarpa has multiple pharmacological effects and is widely used in the prevention and treatment of migraine, diabetes, cardiovascular disease, cancer, and other chronic diseases; however, the pharmacological effects of its active compound evodiamine (Evo) have not been thoroughly investigated. The purpose of this study was to investigate the effects of Evo on antiplatelet activation and thrombosis. We discovered that Evo effectively inhibited collagen-induced platelet activation but had no effect on platelet aggregation caused by activators such as thrombin, ADP, and U46619. Second, we found that Evo effectively inhibited the release of platelet granules induced by collagen. Finally, evodiamine inhibits the transduction of the SFKs/Syk/Akt/PLCγ2 activation pathway in platelets. According to in vivo studies, Evo significantly prolonged the mesenteric thromboembolism induced by ferric chloride and had no discernible effect on the coagulation function of mice. In conclusion, the antiplatelet and thrombotic effects of Evo discovered in this study provide an experimental basis for the investigation of the pharmacological mechanisms of Evo and the development of antiplatelet drugs.

POS0852 SYMPTOMS OF GASTROESOPHAGEAL REFLUX ARE A BETTER PREDICTOR OF SYSTEMIC SCLEROSIS-RELATED INTERSTITIAL LUNG DISEASE PROGRESSION THAN QUANTITATIVE RADIOGRAPHIC ASSESSMENT OF ESOPHAGEAL PARAMETERS

Background

Esophageal dysfunction affects the majority of patients with systemic sclerosis (SSc). Gastroesophageal reflux (GERD)-associated microaspiration may serve as an inciting and/or exacerbating factor in the pathogenesis of interstitial lung disease (ILD) in SSc. Few studies have investigated the relationship between objective measures of esophageal involvement in SSc and the progression of SSc-ILD.

Objectives

(1) To investigate whether patient-reported symptoms of GERD predict SSc-ILD severity and progression; (2) To explore whether quantitative radiographic measurements of esophageal parameters predict SSc-ILD severity and progression.

Methods

Participants of Scleroderma Lung Study (SLS) II (24 months of mycophenolate versus 12 months cyclophosphamide followed by 12 months of placebo in patients with active SSc-ILD) were included.1 The UCLA SCTC GIT 2.0 was used to assess the severity of reflux at baseline. Quantitative image analysis was used to calculate the diameter and area of the esophagus in the area of maximum dilation. Univariate and multivariable linear regression analyses were used to evaluate the relationship between baseline reflux scores/esophageal parameters and the severity and progression of SSc-ILD based on the quantitative radiographic extent of ILD (QILD) and fibrosis (QLF) in the lobe of maximum involvement (LM). All multivariable models controlled for treatment arm and baseline ILD severity, as well as proton pump inhibitor (PPI) use.

Results

Among the 141 of 142 SLS II participants with patient-reported reflux scores at baseline, the mean score was 0.57, indicating moderate reflux. The mean maximal esophageal diameter and area at baseline were 22 mm and 242 mm2, respectively. There were no significant correlations between reflux scores, esophageal diameter, esophageal area and QILD-LM and QLF-LM at baseline. However, in the 96 participants with HRCT scans available at 24 months, increased reflux scores were significantly associated with worsening of QLF-LM and QILD-LM (Figure 1). Even after controlling for disease severity at baseline, treatment arm and PPI use, reflux scores remained significantly associated with change in QLF-LM (P-value 0.05) and QILD-LM (P-value 0.003). Neither the maximum esophageal area, nor the maximum esophageal diameter was associated with the change in QILD-LM or QLF-LM in univariate or multivariate analyses.

Figure 1.

Increased reflux scores at baseline are associated with increased progression (worsening) of QILD (A) and QLF (B) in the lobe of maximum involvement in patients with SSc-ILD.

Conclusion

Increased self-reported reflux was independently associated with worsening radiographic fibrosis and ILD in patients receiving treatment for SSc-ILD. The maximum esophageal diameter and esophageal area did not correlate with reflux scores and did not predict severity or progression of SSc-ILD. These findings illustrate the importance of eliciting a careful patient history of reflux symptoms in patients with ILD and further highlight the need for improved objective measures of esophageal dysfunction in SSc.

References

[1]Tashkin et al. Lancet Resp Med 2016.

Disclosure of Interests

Elizabeth Volkmann Speakers bureau: Boehringer Ingelheim, Consultant of: Boehringer Ingelheim, Grant/research support from: Forbius, Horizon, Kadmon, Boehringer Ingelheim, Donald Tashkin: None declared, Mei Leng: None declared, Grace Kim: None declared, Jonathan Goldin: None declared, Michael Roth Grant/research support from: Genentech

[Research advances on the biomechanical micro- environment facilitated wound repair through the regulation of cell migration]

Biomechanical microenvironment refers to a variety of mechanical signals in the extracellular mechanical microenvironment, which will change correspondingly with time and space. It plays an important role in histological changes such as cell migration, proliferation, and differentiation, and can further affect wound healing. Wound healing is a complex pathophysiological process, and one of the important factors that affects wound healing is whether the cells can efficiently and quickly migrate to the wound center or not. Previous studies have shown that biomechanical microenvironment can not only induce the directional migration of cells, but also improve the migration rate of cells. In the complex natural environment, cells adopt various migration patterns and are dominated by special patterns such as local myosin contractility and extracellular microenvironment. In addition to overcoming the extracellular barrier, cells also need to interact with neighboring cells and tissue through local physical and mechanical forces and signals to complete migration and thus accelerate wound healing. Therefore, in recent years, scholars at home and abroad have been actively developing biological materials based on improving biomechanical microenvironment in order to further promote cell migration and thus accelerate wound healing. This paper reviews the recent research advances on the role of biomechanical environment in wound healing promotion via the regulating of cell migration and the development of related biomaterials.

Applying a Psychological Nursing Care Quality Evaluation Index in hospitalized patients: A pilot study

Psychological problems have become a significant public health problem. Appropriate mental health care is crucial in promoting patient care quality. This study aimed to test the feasibility of a Psychological Nursing Quality Evaluation Index in hospitalized patients. This is a pilot study with patients hospitalized with myocardial infarction from July to September 2020 in China. The researchers used an observational approach to examine nurses' psychological health care performance based on the Psychological Nursing Quality Evaluation Index. The results indicated high compliance rates of nurses' psychological care performance, which provides references for evaluating and monitoring inpatient psychological nursing care.

OP0268 TREATMENT STATUS AFFECTS HOW PULMONARY BIOMARKERS PREDICT PROGRESSION OF SYSTEMIC SCLEROSIS-RELATED INTERSTITIAL LUNG DISEASE

Background:

The course of interstitial lung disease (ILD) varies considerably in patients with systemic sclerosis (SSc), and no biomarkers have been found to consistently predict ILD progression in this population. Treatment may affect how a candidate biomarker correlates with improvement/worsening of SSc-ILD. We hypothesized that specific proteins recovered from bronchoalveolar lavage (BAL) would differentially predict progression of SSc-ILD based on whether a patient was receiving ILD therapy.

Objectives:

(1) To assess the relationship between 68 unique BAL proteins measured in participants of Scleroderma Lung Study (SLS) I1 and changes in radiographic extent of SSc-ILD; (2) To determine if treatment affects whether a specific protein predicts improvement or worsening of SSc-ILD.

Methods:

Bronchoscopy was performed on 144 of the 158 participants in SLS I (Cyclophosphamide [CYC] vs. placebo) with 103 BAL samples available for analysis. BAL was lyophilized, concentrated 10X and used in a multiplex protein analysis of 68 distinct cytokines, chemokines and growth factors. Quantitative imaging analysis (QIA) was used to calculate the extent of radiographic fibrosis (QLF) in the whole lung using HRCT of the chest at baseline and 12 months. Multivariable linear regression models were created to determine the key BAL proteins associated with change in QLF scores using a backward selection process adjusting for treatment arm and ILD severity. The bootstrap procedure was employed for internal validation.

Results:

A number of BAL proteins were significantly associated with change in QLF scores at 12 months; however, the directionality of these associations was often based on the presence/absence of treatment. For example, increased levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-1, monocyte chemoattractant protein (MCP)-3, chemokine ligand (CCL)-5, transforming growth factor (TGF)-β, hepatocyte growth factor (HGF), stem cell factor (SCF), IL-4, TGF-α, were associated with worse QLF scores in patients who received placebo; whereas, increased levels of these same proteins were associated with improved QLF scores in patients who received CYC (Figure). Increased levels of Fractalkine were associated with worse in QLF scores, and increased levels of IL-7 were associated with improved QLF scores, regardless of treatment arm. In the multivariable model adjusting for treatment arm and baseline severity of ILD, IL-1, MCP-3, surfactant protein C, IL-7, and CCL-5 were independently associated with change in QLF scores.

Figure 1.

Example of a specific BAL protein (GM-CSF) that predicts worse QLF scores in patients receiving placebo (Group B, Red dotted line) and improved QLF scores in patients receiving CYC (Group A, Blue solid line). Shaded areas represent 95% confidence intervals.

Conclusion:

Proteins that mediate both inflammation and fibrosis differentially affected progression of SSc-ILD based on treatment status. Higher levels of certain proteins predicted worsening of ILD in patients receiving placebo, but improvement in patients receiving CYC. Measuring these proteins could help to identify patients who: (1) are at risk for ILD progression, and (2) may preferentially benefit from treatment with immunosuppression.

References:

[1]Tashkin DP, et al. NEJM 2006.

Disclosure of Interests:

Elizabeth Volkmann Consultant of: Boehringer Ingelheim, Grant/research support from: Corbus, Forbius, Donald Tashkin: None declared, Mei Leng: None declared, Ning Li: None declared, Grace Kim: None declared, Jonathan Goldin: None declared, Airi Harui: None declared, Michael Roth Grant/research support from: Genentech/Roche

Experimental Study on the Effect of Allogeneic Endothelial Progenitor Cells on Wound Healing in Diabetic Mice

Endothelial progenitor cells (EPCs) are involved in the neovascularization in traumatic and ischemic sites, but EPCs are "detained" in bone marrow under diabetic conditions, which results in reduction of the number of EPCs and their biological activity in peripheral blood. Based on our previous study to mobilize autologous bone marrow EPCs by administering AMD3100+G-CSF to realize the optimal effect, our present study is aimed at exploring the effects of transplanting EPCs locally in a wound model of diabetic mice. First, we prepared and identified EPCs, and the biological functions and molecular characteristics were compared between EPCs from DB/+ and DB/DB mice. Then, we performed full-thickness skin resection in DB/DB mice and tested the effect of local transplantation of EPCs on skin wound healing. The wound healing process was recorded using digital photographs. The animals were sacrificed on postoperative days 7, 14, and 17 for histological and molecular analysis. Our results showed that DB/+ EPCs were biologically more active than those of DB/DB EPCs. When compared with the control group, local transplantation of EPCs accelerated wound healing in DB/DB mice by promoting wound granulation tissue formation, angiogenesis, and collagen fiber deposition, but there was no significant difference in wound healing between DB/+ EPCs and DB/DB EPCs transplanted into the wound. Furthermore, local transplantation of EPCs promoted the expression of SDF-1, CXCR4, and VEGF. We speculated that EPC transplantation may promote wound healing through the SDF-1/CXCR4 axis. This point is worth exploring further. Present data are of considerable significance because they raise the possibility of promoting wound healing by isolating autologous EPCs from the patient, which provides a new approach for the clinical treatment of diabetic wounds in the future.

[Research advances on assisted analgesic and sedative treatment of burn children]

Burn children would experience pain and anxiety during treatment and rehabilitation, thus analgesic and sedative treatment should be applied throughout the whole process of burn treatment. Due to the unique physiological and psychological status of burn children, analgesic and sedative treatment for burn children is a relatively complex process compared with that for adult burn patients. Therefore, how to provide the effective and safe analgesic and sedative treatment for burn children is a clinical challenge. This paper reviewed the related progress of assisted analgesic and sedative treatment of burn children, in order to provide a reference for clinical treatment.

Mental distress and influencing factors in nurses caring for patients with COVID-19

BACKGROUND

Nurses are experiencing tremendous stress during the new coronavirus disease 2019 (COVID-19) pandemic, especially intensive care nurses. The pandemic of the disease is a tragedy, which may leave a catastrophic psychological imprint on nurses. Understanding nurses' mental distress can help when implementing interventions to mitigate psychological injuries to nurses.

AIMS AND OBJECTIVES

To quantify the severity of nurses' post-traumatic stress disorder (PTSD) symptoms and stress and explore the influencing factors of their psychological health when caring for patients with COVID-19.

DESIGN

A cross-sectional survey.

METHODS

The PTSD Checklist-Civilian and the Perceived Stress Scale were administered from 11 to 18 March 2020, to 90 nurses selected from another city to go and help an intensive care unit (ICU) in Wuhan, China. These nurses were selected because of their high levels of clinical performance and resilience status.

RESULTS

Nurses' average PTSD score was 24.62 ± 6.68, and five (5.6%) of the nurses reported a clinically significant level of PTSD symptoms (>38 points). Nurses' perceived stress averaged 19.33 ± 7, and 20 nurses (22.22%) scored positively >25 points. Nurses' stress and PTSD symptoms were positively correlated (P < .01). Major stress sources included working in an isolated environment, concerns about personal protective equipment shortage and usage, physical and emotional exhaustion, intensive workload, fear of being infected, and insufficient work experiences with COVID-19.

CONCLUSIONS

This study showed that even relatively highly resilient nurses experienced some degree of mental distress, including PTSD symptoms and perceived stress. Our findings highlight the importance of helping nurses cultivate resilience and reduce stress.

RELEVANCE TO CLINICAL PRACTICE

Recommendations for practice include providing adequate training and orientation before assigning nurses to ICU to help, offering disaster-emergency-preparedness training to keep nurses prepared, providing caring and authentic nursing leadership, offering ongoing psychological support to frontline nurses.

The prevalence of intestinal helminth infection in rural subdistricts of northeastern Thailand

This study aimed to determine the prevalence and intensity of intestinal helminth infections (IHIs) among rural villagers in Waeng Noi district, Khon Kaen Province, northeastern Thailand. A cross-sectional study was conducted between March 1 and July 30, 2018, among rural villagers from 30 rural villages in 2 subdistricts. The participants were selected from the village enrollment list after proportional allocation of the total sample size. The background characteristic data were collected using a structured questionnaire. Specimens from patients with IHIs were prepared by concentration with a Faecal Parasite Concentrator-Solvent-Free (Mini Parasep® SF), and helminths were then detected using a light microscope. Of the 400 faecal specimens examined, 23 were positive for at least one intestinal helminth, resulting in a prevalence of 5.75%. The most prevalent helminths were Taenia spp., 10 (2.50%); followed by hookworm, 5 (1.25%); Trichuris trichiura, 4 (1.0%); Ascaris lumbricoides, 3(0.50%); and Opisthorchis viverrini, 1 (0.25%). All infected participants had a light intensity of IHI. Location (adjusted OR=2.52; 95% CI=1.30-3.52; P =0.042) showed a significant association with the prevalence of intestinal helminths. This study reveals that IHIs, particularly those with foodborne and soil-transmitted species of helminths, are prevalent in adults in rural subdistricts. A greater focus on interventions to improve personal hygiene and sanitation to prevent the spread of IHIs is required. Further studies should be performed to implement interdisciplinary research approaches in the study area.

Abstract P5-08-01: DPYSL3 modulates mitosis, migration and epithelial to mesenchymal transition in claudin-low breast cancer

Proteogenomics is the field of integrating data from mass spectrometry-based shotgun proteomics, and phosphoproteomics into next-generation RNA and DNA sequencing data analysis pipelines that promises new insights into cancer biology and therapeutic targeting. As well as analyses of clinical samples for disease phenotype association analysis, the application of proteogenomics to model systems also has considerable potential. A Clinical Proteomic Tumor Analysis Consortium (CPTAC) proteogenomic analysis prioritized dihydropyrimidinase-like-3 (DPYSL3) as a multi-level (RNA/Protein/Phosphoprotein) expression outlier specific to the Claudin-Low (CLOW) subset of triple negative breast cancers. A Pubmed informatics tool indicated a paucity of data in the context of breast cancer which further prioritized DPYSL3 for study.

DPYSL3 was identified as a protein that is regulated during neuronal differentiation in the cerebral cortex and in neuronal cell lines and plays a role in regulating neurite outgrowth somehow through an association with vesicles in the growth cone. In addition, DPYSL3 expression has been observed in several malignant tumors, including prostate cancer, pancreatic cancer, gastric cancer and neuroblastoma. DPYSL3 is reported to play a role in cell migration and metastasis suppression in prostate cancer. However, in pancreatic cancer, DPYSL3 is positively associated with liver metastasis and poor outcome.

DPYSL3 knock-down in DPYSL3 (+) CLOW cell lines demonstrated reduced proliferation, yet enhanced motility and increased expression of Epithelial to Mesenchymal Transition (EMT) markers suggesting that DPYSL3 is a multi-functional signaling modulator. Slower proliferation in DPYSL3 (-) CLOW cells was associated with accumulation of multi-nucleated cells indicating a mitotic defect that was associated with a collapse of the vimentin (VIM) microfilament networkinduced by VIM hyperphosphorylation. On the other hand, DPYSL3 suppressed the expression of EMT regulators TWIST and SNAIL and opposed p21 activated kinase 2 (PAK2) dependent migration, but these EMT regulators in turn induced DPYSL3 expression, suggesting DPYSL3 participates in negative feedback in EMT. Cell migration in DPYSL3 (-) cells correlated with increased phosphorylation of PAK2 on Ser20 and was sensitive to PAK2 siRNA and pharmacological PAK inhibition.Immunoprecipitation and mass spectrometry-based proteomics or western blotting strongly suggests that PAKs interact such that DPYSL3 may function as a direct negative regulator of PAK family kinases. Thus, a PAK inhibitor could potentially mitigate increase migration as an adverse effect of DPYSL3 suppression.

In conclusion, DPYSL3 is a remarkable multifunctional signaling scaffold that should be examined further to provide insights into the stem cell-like state of claudin-low breast cancers, particularly in terms of their cell cycle dependencies, migratory activity and capacity for EMT.

Citation Format: Matsunuma R, Chan DW, Kim B-J, Singh P, Han A, Saltzman A, Cheng C, Lei JT, Sahin E, Leng M, Fan C, Perou CM, Malovannaya A, Ellis MJ. DPYSL3 modulates mitosis, migration and epithelial to mesenchymal transition in claudin-low breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-08-01.

Assessment of Palliative Care Needs in Hospital Settings in Rwanda

Background: Rwanda is among the first African countries with a palliative care (PC) policy and implementation plan. A partnership with the Ministry of Health (MoH) through the Rwanda Biomedical Centre (RBC) and the University of Edinburgh has supported an integrated approach including expanding the evidence base. Aim: To assessing the need for (PC) to inform policy, service delivery and training. Methods: A point prevalence PC needs assessment was conducted in nine public hospitals (referral, provincial and district). A records census identified those with life-limiting illness (LLI) who were then invited to participate by interview. The assessment tool included the APCA African POS, POS S, WHO performance status and demographic information. Results: 608 case notes were reviewed, 152 eligible and 124 completed assessment. 25% of all patients admitted had LLI, of which 99.2% had evidence of unmet need determined by at least one score on the APCA POS ≥ 3. Diagnoses 29% cancer, 29% cardiovascular disease, 16.9% end-stage organ failure and 13.7% HIV. Symptoms with greatest impact; nausea and vomiting (34.7%) and pain (32.3%). 63.7% with WHO performance status 4 or 5. 8.1% seen by existing PC services. Conclusion: Although the MoH and RBC are making bold steps toward developing PC in Rwanda, there remains a significant amount of unmet PC needs. Meeting this need requires recognition of the scope of PC needs beyond cancer, feedback to the hospitals and health care workers, thinking strategically how to further strengthen the health system and further capacity building and training.

Home-Based Care Practitioners: A Strategy for Continuum of Care for Very Ill Patient

Background: Rwanda Ministry of Health in collaboration with partners has initiated an innovative initiative named Home Based Care Practitioners (HBCPs) to respond to the burden of long-term hospitalization for end of life patients. Aim: The program aims at providing home-based care to accompany patients and their families in their home, reduce unnecessary pain and suffering for those with chronic or terminal conditions, provide counseling to the patients and their families, early diagnosis of NCDs and improve awareness on prevention of NCDs risk factors and effectively refer them to either health facilities or community-based resources that can be of further help. Methods: The HBCPs is implemented into phases; phase one has started with a pilot of 200 HBCPs in 100 cells surrounding nine provincial and referral hospitals of Rwanda; 2 practitioners for both gender in each cell, with a criteria of completion at least secondary school. They have undergone a training of 120 credits (900 hours), equivalent of four months for theory and two months of practice. After training they have been deployed into the community with a supervision of health centers in collaboration with hospitals and Rwanda Biomedical Center. Results: During the implementation period of 6 months, 1663 NCDs patients have been transferred from health facility (OPD) to HBCPs for routine follow-up, 482 palliative care patients have been reported on end of life care by HBCPs, there is a remarkable linkage between facilities and community care ensured by supervisory relationship between health services providers and home based care practitioners, long-term admission has reduced the cost for the family and the facility due to the discharge of care from hospital to home. Conclusion: In a limited setting of social and economic cost of providing frivolous care in an expensive hospital for chronic or terminal conditions that would be better managed through treatment or palliative care at home (or less acute setting) home based care effort can better meet the needs of Rwandans at the community level and has started to show the efficiency in providing quality care to people in need of palliative care.

Novel hydroxybutyl chitosan nanoparticles for siRNA delivery targeting tissue factor inhibits proliferation and induces apoptosis in human vascular smooth muscle cells

Chitosan, a polysaccharide isolated from shrimp and other crustacean shells, has been widely investigated for DNA and siRNA delivery. Despite substantial effort having been made to improve chitosan as a non-viral gene delivery vector, the application is severely limited by its poor solubility under physiological conditions. Hydroxybutyl chitosan (HBC), a modified chitosan, is soluble under neutral conditions. Tissue factor (TF) is involved in the pathogenesis of cardiovascular diseases by promoting thrombus formation and inducing the migration and proliferation of vascular smooth muscle cells. Targeting TF is an attractive therapeutic strategy for cardiovascular diseases. In the present study, the use of HBC for the transfer of TF-siRNAs into human umbilical vein smooth muscle cells (HUVSMCs) was investigated, and the effects of TF knockdown on cell proliferation and apoptosis were examined. HBC/siRNA nanoparticles were produced by mixing HBC and siRNA solutions with the assistance of tripolyphosphate buffer. The transfection efficiency with these nanoparticles was 74±2.5%, which was determined using a fluorescence-labeled siRNA under fluorescence microscopy. The delivery of HBC/TF-siRNA resulted in reductions in the production of cellular and soluble TF protein in HUVMSCs, which were measured using western blotting and enzyme-linked immunosorbent assay, respectively. TF knockdown led to inhibited cell proliferation, as assessed using a Cell Counting Kit-8 assay, and increased cell apoptosis, determined using Annexin V-fluorescein isothiocyanate staining. These findings suggested that HBC may be a promising vector for siRNA delivery, and that in vivo HBC/siRNA nanoparticle delivery targeting TF may be a potential option for the treatment of cardiovascular diseases, which warrants further investigation.

Percutaneous extraction of leads from coronary sinus vein and branch by modified techniques

BACKGROUND

Cardiac resynchronization therapy (CRT) device and coronary sinus (CS) lead extraction are required due to the occurrence of systemic infection, malfunction, or upgrade. Relevant research of CS lead extraction is rare, especially in developing countries because of the high cost and lack of specialized tools. We aimed to evaluate percutaneous extraction of CS leads by modified conventional techniques.

METHODS

Of 200 patients referred for lead extraction from January 2007 to June 2011, 24 (12.0%) involved CS leads (24 CS leads). We prospectively analyzed clinical characteristics, optimized extraction techniques and feasibility of extraction.

RESULTS

Complete procedural success was achieved in 23 patients (95.8%), and the clinical success in 24 patients (100.0%). The leading indication for CS lead extraction was infection (66.7%). Mean implant duration was (29.5 ± 20.2) months (range, 3 - 78 months). Sixteen CS leads (66.6%) were removed with locking stylets plus manual traction by superior transvenous approach. Mechanical dilatation and counter-traction was required to free fibrotic adhesions and extract 4 CS leads (16.7%), which had longer implant duration than other leads ((62.5 ± 12.3) vs. (22.9 ± 14.1) months, P < 0.05). Another 4 CS (16.7%) leads were removed by modified and innovative snare techniques from femoral vein approach. Median extraction time was 11 minutes (range, 3 - 61 minutes) per CS lead, which had significant correlation with implant duration (r = 0.8, P < 0.001). Sixteen patients (66.6%) were reimplanted with new devices at a median of 7.5 days after extraction. Median followed-up was 23.5 months (range, 8 - 61 months), three patients died due to sudden cardiac death (26 months), heart failure (45 and 57 months, respectively).

CONCLUSION

The modified procedure was proved to be practical for percutaneous extraction of CS leads, especially in developing countries lacking expensive powered sheaths.

Risk of cardiovascular disease in first and second generation Mexican-Americans

This study examines the cardiovascular disease (CVD) risk profiles of first generation (FG) and second generation (SG) Mexican-Americans (MA) in two large national studies--the Hispanic Health and Nutrition Examination Study (HHANES) (1982-1984) and the National Health and Examination Study (NHANES) (1999-2004). The main outcome measures were five individual risk indicators of CVD (total cholesterol, HDL cholesterol, hypertension, diabetes, and smoking) and a composite measure (the Framingham Risk Score [FRS]). The analyses included cross-survey (pseudocohort) and within-survey (cross-sectional) comparisons. In multivariate analyses, SG men had higher rates of hypertension and lower rates of smoking than FG men; and SG women had lower total cholesterol levels, higher rates of hypertension, and lower rates of smoking than FG women. There was no generational difference in the FRS in men or women. The cross-survey comparisons detected generational differences in CVD risk factors not detected in within-survey comparisons, particularly among MA women. Future studies of generational differences in risk should consider using pseudocohort comparisons when possible.

Weight loss and changes in generic and weight-specific quality of life in obese adolescents

PURPOSE

To investigate how weight loss correlates with changes in generic and weight-specific quality of life (QoL).

METHODS

Youth generic (YQOL-S) and weight-specific instruments (YQOL-W) from 133 youth age 11-19 were analyzed at the beginning and end of 4-week immersion camp sessions known to produce weight loss. Paired samples t tests were used to test mean difference between baseline and final Body Mass Index (BMI) and YQOL-S and YQOL-W scores. YQOL-S and YQOL-W scores were transformed to values between 0 and 100, with higher values indicating better QOL. Cohen's d effect sizes were calculated to assess magnitude of effects. Percent weight loss (as % of baseline weight), change in BMI (baseline kg/m²-follow-up kg/m²), and change in % overweight ((BMI-50th% BMI for age and sex)/50th% BMI for age and sex × 100) were calculated. Multiple regressions were used to model final YQOL scores in the 11-14 and 15-19 age groups as functions of each measure of weight change, sex, age, and baseline YQOL score.

RESULTS

Youth experienced significant reductions in BMI (Mean change = 3.7, SD = 1.4, t = 34.1, P < 0.001) and in the other measures of weight change. YQOL-S and YQOL-W scores improved significantly (P < 0.001), and effect sizes were 0.61 and 0.66, respectively.

CONCLUSION

Changes in generic and weight-specific quality of life scores are associated with weight loss. The weight-specific measure is slightly more sensitive to weight changes; however, when controlling for modifiers, the YQOL-W remained significantly associated with weight loss, while the generic QoL measure did not.

Overexpression of the Arabidopsis thaliana MinD1 gene alters chloroplast size and number in transgenic tobacco plants

The Arabidopsis thaliana (L.) Heynh. minD gene (AtMinD1) was isolated and constitutively expressed in tobacco (Nicotiana tabacum L.) plants using the CaMV 35S promoter. Confocal and electron-microscopic analysis of the AtMinD1 transgenic tobacco lines revealed that the chloroplasts were abnormally large and fewer in number compared with wild-type tobacco plants. The abnormal chloroplasts were less prevalent in guard cells than in mesophyll cells. Chloroplast and nuclear gene expression was not significantly different in AtMinD1-overexpressing plants relative to wild-type tobacco plants. Chloroplast DNA copy number was not affected, based on the relative level of the rbcL gene in transgenic plants. Transgenic tobacco plants constitutively overexpressing AtMinD1 were completely normal phenotypically with respect to growth and development, and also displayed normal photosynthetic electron transport rates. These results show that the Arabidopsis MinD1 gene also functions in a heterologous system and confirm the role of the MinD protein in regulation of chloroplast division.

Antibodies to N-hydroxy-2-aminofluorene modified DNA as probes in the study of DNA reacted with derivatives of 2-acetylaminofluorene

Antibodies were elicited in rabbits immunized with a mixture of methylated bovine serum albumin and N-hydroxy-2-aminofluorene reacted DNA (DNA-AF). These antibodies were used in competition radioimmunoassays (RIA) with [3H]DNA-AF as radioactive antigen and different N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) and N-hydroxy-2aminofluorene (N-OH-AF) reacted DNAs, deoxyguanosine, dGMP, dGpA and dApG as inhibitors. Based on the results of RIA it is concluded that the binding sites of the two residues, -AF and -AAF, to guanosine in DNA, are essentially the same. Moreover, the same sites seem to be reactive also in the direct reaction of N-AcO-AAF with dGMP. Circular dichroism measurements of modified DNA confirm the RIA results.

DSP1, an HMG-like protein, is involved in the regulation of homeotic genes

The Drosophila dsp1 gene, which encodes an HMG-like protein, was originally identified in a screen for corepressors of Dorsal. Here we report that loss of dsp1 function causes homeotic transformations resembling those associated with loss of function in the homeotic genes Sex combs reduced (Scr), Ultrabithorax (Ubx), and Abdominal-B. The expression pattern of Scr is altered in dsp1 mutant imaginal discs, indicating that dsp1 is required for normal expression of this gene. Genetic interaction studies reveal that a null allele of dsp1 enhances trithorax-group gene (trx-G) mutations and partially suppresses Polycomb-group gene (Pc-G) mutations. On the contrary, overexpression of dsp1 induces an enhancement of the transformation of wings into halteres and of the extra sex comb phenotype of Pc. In addition, dsp1 male mutants exhibit a mild transformation of A4 into A5. Comparison of the chromatin structure at the Mcp locus in wild-type and dsp1 mutant embryos reveals that the 300-bp DNase I hypersensitive region is absent in a dsp1 mutant context. We propose that DSP1 protein is a chromatin remodeling factor, acting as a trx-G or a Pc-G protein depending on the considered function.

GreA and GreB proteins revive backtracked RNA polymerase in vivo by promoting transcript trimming

The GreA and GreB proteins of Escherichia coli show a multitude of effects on transcription elongation in vitro, yet their physiological functions are poorly understood. Here, we investigated whether and how these factors influence lateral oscillations of RNA polymerase (RNAP) in vivo, observed at a protein readblock. When RNAP is stalled within an (ATC/TAG)(n) sequence, it appears to oscillate between an upstream and a downstream position on the template, 3 bp apart, with concomitant trimming of the transcript 3' terminus and its re-synthesis. Using a set of mutant E.coli strains, we show that the presence of GreA or GreB in the cell is essential to induce this trimming. We show further that in contrast to a ternary complex that is stabilized at the downstream position, the oscillating complex relies heavily on the GreA/GreB-induced 'cleavage-and-restart' process to become catalytically competent. Clearly, by promoting transcript shortening and re-alignment of the catalytic register, the Gre factors function in vivo to rescue RNAP from being arrested at template positions where the lateral stability of the ternary complex is impaired.

Replacement of an NH(3) by an iminoether in transplatin makes an antitumor drug from an inactive compound

To investigate the modifications of antitumor activity and DNA binding mode of transplatin after replacement of one nonleaving group NH(3) by an iminoether group, trans-[PtCl(2)(Z-HN=C(OMe)Me)(NH(3)] and trans-[PtCl(2)(E-HN=C(OMe)Me)(NH(3)] complexes (differing in the Z or E configuration of iminoether, and abbreviated mixed Z and mixed E, respectively), have been synthesized. In a panel of human tumor cell lines, both mixed Z and mixed E show a cytotoxic potency higher than that of transplatin, the mean IC(50) values being 103, 37, and 215 microM, respectively. In vivo mixed Z is more active and less toxic than mixed E in murine P388 leukemia and retains its efficacy against SK-OV-3 human cancer cell xenograft in nude mice. In the reaction with naked DNA, mixed Z forms monofunctional adducts that do not evolve into intrastrand cross-links but close slowly into interstrand cross-links between complementary guanine and cytosine residues. The monofunctional mixed Z adducts are removed by thiourea and glutathione. The interstrand cross-links behave as hinge joints, increasing the flexibility of DNA double helix. The mixed Z, transplatin, and cisplatin interstrand cross-links, as well as mixed Z monofunctional adducts are not specifically recognized by HMG1 protein, which was confirmed to be able to specifically recognize cisplatin d(GpG) intrastrand cross-links. These data demonstrate that the DNA interaction properties of the antitumor-active mixed Z are very similar to those of transplatin, thus suggesting that clinical inactivity of transplatin could not depend upon its peculiar DNA binding mode.

Parallel-stranded DNA with Hoogsteen base pairing stabilized by a trans-[Pt(NH3)2]2+ cross-link: characterization and conversion into a homodimer and a triplex

The oligonucleotides 5'-d(TTTTCTTTTG) and 5'-d(AAAAGAAAAG) were cross-linked with a trans-[Pt(NH3)2]2+ entity via the N7 positions of the 3'-end guanine bases to give parallel-stranded (ps) DNA. At pH 4.2, CD and NMR spectroscopy indicate the presence of Hoogsteen base pairing. In addition, temperature-dependent UV spectroscopy shows an increase in melting temperature for the platinated duplex (35 degrees C) as compared to the non-platinated, antiparallel-stranded duplex formed from the same oligonucleotides (21 degrees C). A monomer-dimer equilibrium for the platinated 20mer is revealed by gel electrophoresis. At pH 4.2, addition of a third strand of composition 5'-d(AGCTTTTCTTTTAG) to the ps duplex leads to the formation of a triple helix with two distinct melting points at 38 degrees C (platinum cross-linked Hoogsteen part) and 21 degrees C (Watson-Crick part), respectively.

Transplatin-modified oligonucleotides as modulators of gene expression

Transplatin [trans-diamminedichloroplatinum(II)], contrary to its stereoisomer cisplatin, is clinically inactive. However, like cisplatin, it binds to DNA. In the first part of this review, some results on the interactions between transplatin and double-stranded DNA are presented. The major bifunctional adducts are interstrand cross-links. Intrastrand cross-links are not formed. On the other hand, intrastrand cross-links are formed in the reaction between single-stranded DNA and transplatin. Some properties of the intrastrand cross-links at GNG sites (N is a nucleotide) are described. The (G1,G3)-intrastrand cross-links rearrange into interstrand cross-links as soon as the platinated oligonucleotides are paired with their complementary strands. The linkage isomerization reaction is exclusively triggered by the formation of a double helix. The potential use of these platinated oligonucleotides to block the cellular machinery specifically and irreversibly is discussed.

HMG boxes of DSP1 protein interact with the rel homology domain of transcription factors

Formation of the dorsoventral axis in Drosophila melanogaster is mediated through control of the expression of several genes by the morphogen Dorsal. In the ventral part of the embryo Dorsal activates twist and represses zen amongst others. Recently, several proteins have been shown to assist Dorsal in the repression of zen, one of which is DSP1, a HMG box protein that was isolated as a putative co-repressor of Dorsal. In this report we used a DSP1 null mutant to ascertain in vivo the involvement of DSP1 in Dorsal-mediated repression of zen but not in the activation of twist. We show that Dorsal has the ability to interact with DSP1 in vitro as well as with rat HMG1. Using truncated versions of the proteins we located the domains of interaction as being the HMG boxes for DSP1 and HMG1 and the Rel domain for Dorsal. Finally, studies of the zen DNA binding properties of Dorsal and another related Rel protein (Gambif1 from Anopheles gambiae) revealed that their DNA binding affinities were increased in the presence of DSP1 and HMG1.

Inhibition of in vitro and ex vivo translation by a transplatin-modified oligo(2'-O-methylribonucleotide) directed against the HIV-1 gag-pol frameshift signal

A 2'-O-methylribooligonucleotide containing a G1.U.G3 triad modified by trans-diamminedichloro-platinum(II) was targeted to the RNA region responsible for the gag-pol frameshifting during translation of the HIV-1 mRNA. The binding of the platinated oligonucleotide to its target RNA induced a rearrangement of the (G1, G3)-intrastrand crosslink, leading to the formation of an intermolecular oligonucleotide-RNA G-A crosslink. This resulted in the selective arrest of translation of a luciferase gene placed downstream of the HIV-1 frameshift signal both in a cell-free extract (rabbit reticulocyte lysate) and in RNA-transfected cells. A specific inhibition of luciferase activity was still observed when the oligonucleotide-RNA complex was not pre-formed prior to either translation or transfection. Moreover, a selective inhibition was also observed when the oligonucleotide and the plasmid DNA encoding the luciferase and bearing the RNA gag- pol frameshifting signal were co-transfected in NIH 3T3 cultured cells. Therefore the intra-strand-->interstrand conversion of the platinum crosslink kinetically competes with the translation machinery and blocks the polypeptide elongation. These transplatin-modified oligonucleotides which operate within a live cell on a 'real-time' basis and do not need an external triggering signal constitute a promising new class of selective reactive probes.

NMR solution structure of a DNA dodecamer containing a transplatin interstrand GN7-CN3 cross-link

The DNA duplex d(CTCTCG*AGTCTC).d(GAGAC-TC*GAGAG) containing a single trans- diammine-dichloroplatinum(II) interstrand cross-link (where G* and C* represent the platinated bases) has been studied by two-dimensional NMR. All the exchangeable and non-exchangeable proton resonance lines were assigned (except H5'/H5") and the NOE intensities were transformed into distances via the RELAZ program. By combining the NOESY and COSY data (330 constraints) and NMR-constrained molecular mechanics using JUMNA, a solution structure of the cross-linked duplex has been determined. The duplex is distorted over two base pairs on each side of the interstrand cross-link and exhibits a slight bending of its axis ( approximately 20 degrees ) towards the minor groove. The platinated guanine G* adopts a syn conformation. The rotation results in a Hoogsteen-type pairing between the complementary G(6)* and C(19)* residues which is mediated by the platinum moiety and is stabilized by a hydrogen bond between O6(G(6)*) and N4H(C(19)*). The rise between the cross-linked residues and the adjacent residues is increased owing to the interaction between these adjacent residues and the ammine groups of the platinum moiety. These results are discussed in relation to the slow rate of closure of the monofunctional adducts into interstrand cross-links.

Interstrand cross-links of cisplatin induce striking distortions in DNA

In the reaction between cellular DNA and cisplatin, different bifunctional adducts are formed including intrastrand and interstrand cross-links. The respective role of these lesions in the cytotoxicity of the drug is not yet elucidated. This paper deals with the current knowledge on cisplatin interstrand cross-links and presents results on the formation, stability and structure of these adducts. A key step in the studies of these lesions is the recent determination of solution and crystallographic structures of double-stranded oligonucleotides containing a unique interstrand cross-link. The DNA distortions induced by this adduct exhibit unprecedented features such as the location of the platinum residue in the minor groove, the extrusion of the cytosines of the cross-linked d(GpC).d(GpC) site, the bending of the helix axis towards the minor groove and a large DNA unwinding. In addition to a detailed determination of the distortions, the high resolution of the crystal structure allowed us to locate the water molecules surrounding the adduct. The possible implications of this structure for the chemical properties and the cellular processing of cisplatin interstrand cross-links are discussed.

In vitro and in vivo antitumour activity and cellular pharmacological properties of new platinum-iminoether complexes with different configuration at the iminoether ligands

In order to widen our knowledge on antitumour trans-[PtCl2(iminoether)2] complexes, we have synthesised two new derivatives, trans-[PtCl2¿E-HN = C(OEt)Me¿2] (1) and trans-[PtCl2¿Z-HN = C(OEt)Me¿2] (2), which differ in the configuration of the iminoether ligands. Isomer 1 showed an in vitro cytotoxicity similar to that of cisplatin in a panel of human tumour cell lines (mean IC50 = 8 and 7.7 microM, respectively), whereas isomer 2 showed a lower activity (IC50 = 14.3 microM). Both 1 and 2 isomers overcame cisplatin resistance of ovarian cancer cell line A2780/Cp8. In agreement with the n-octanol/saline partition ratios, intracellular platinum content (and DNA platination) after a 2-h exposure to equimolar drug concentrations was in the order 1 > 2 >> cisplatin, thus indicating that substitution of imminoethers for ammines determines a major lipophilicity and cellular uptake of the platinum drug. Both 1 and 2 showed a major toxic effect towards an excision repair-defective Drosophila strain, thus indicating cellular DNA as cytotoxic target. Finally, both 1 and 2 were active in vivo against the murine P388 system, but, contrary to the in vitro activity, isomer 2 was slightly more active than 1. On the whole, the results confirm the antitumour activity of trans-[PtCl2(iminoether)2] complexes, and indicate that the configuration of the iminoether ligands may affect the pharmacological properties of this class of complexes.

In vivo evidence for back and forth oscillations of the transcription elongation complex

We have used a combination of DNA and RNA footprinting experiments to analyze the structural rearrangements experienced by a transcription elongation complex that was halted in vivo by a protein readblock. We show that the complex readblocked within an (ATC/TAG)(n) sequence is in a dynamic equilibrium between upstream- and downstream- translocated conformers. By increasing the strength of the putative RNA-DNA hybrid, the ternary complex is readily trapped in the downstream-translocated conformation, where the melted DNA region is limited to 8 bp. The shift of the equilibrium towards the downstream location is also achieved by introducing within the 5' end of the message an RNA sequence that can pair with a segment of the transcript in the vicinity of the halted ternary complex. Our results demonstrate that within certain template DNA sequences, the back and forth oscillations of the ternary complex actually occur in a multipolymerase system and inside the cell. Furthermore, the cis-acting effect of the upstream RNA sequence underscores an important phenomenon in gene regulation where a transcript may regulate its own elongation.

Cytotoxicity and DNA binding mode of new platinum-iminoether derivatives with different configuration at the iminoether ligands

The platinum-iminoether complexes trans-[PtCl2[E - HN = C(OEt)Me]2] (1) and trans-[PtCl2[Z - HN = C(OEt)Me[2] (2), differing in the configuration of the iminoether ligands, were investigated for cytotoxicity towards human tumor cell lines, the involvement of DNA as a cytotoxic target, and their DNA binding mode. The cytotoxicity of isomer 1 was comparable to that of cisplatin, whereas isomer 2 was slightly less active. Excision-repair-deficient xeroderma pigmentosum group A cells were four times more sensitive to both isomers than normal cells, thus implicating cellular DNA as the cytotoxic target. Replication mapping experiments showed that both isomers interact preferentially with guanine residues at py-G-py sites. Oligodeoxyribonucleotides containing unique N7-guanine monofunctional adducts of the more cytotoxic isomer 1 were prepared and investigated for chemical reactivity, stability and DNA conformational alterations. The results showed that the ability of thiourea to labilize the monofunctional adducts depends upon the DNA secondary structure, but not upon the sequence context. Monofunctional adducts evolve to bidentate adducts in single-stranded oligonucleotides, but they are stable in double-stranded oligonucleotides and produce conformational distortions selectively located at the 5'-adjacent base pair. This study gives new insight into the mechanism of action of trans platinum-iminoether complexes, enabling for the first time comparison between different ligand isomers.

Crystal structure of a double-stranded DNA containing a cisplatin interstrand cross-link at 1.63 A resolution: hydration at the platinated site

cis-diamminedichloroplatinum (II) (cisplatin) is a powerful anti-tumor drug whose target is cellular DNA. In the reaction between DNA and cisplatin, covalent intrastrand and interstrand cross-links (ICL) are formed. Two solution structures of the ICL have been published recently. In both models the double-helix is bent and unwound but with significantly different angle values. We solved the crystal structure at 100K of a double-stranded DNA decamer containing a single cisplatin ICL, using the anomalous scattering (MAD) of platinum as a unique source of phase information. We found 47 degrees for double-helix bending and 70 degrees for unwinding in agreement with previous electrophoretic assays. The crystals are stabilized by intermolecular contacts involving two cytosines extruded from the double-helix, one of which makes a triplet with a terminal G.C pair. The platinum coordination is nearly square and the platinum residue is embedded into a cage of nine water molecules linked to the cross-linked guanines, to the two amine groups, and to the phosphodiester backbone through other water molecules. This water molecule organization is discussed in relation with the chemical stability of the ICL.

Domain-domain interactions in high mobility group 1 protein (HMG1)

The high mobility group protein HMG1 is a conserved chromosomal protein with two homologous DNA-binding domains, A and B, and an acidic carboxy-terminal tail, C. The structure of isolated domains A and B has been previously determined by NMR, but the interactions of the different domains within the complete protein were unknown. By means of differential scanning calorimetry and circular dichroism we have investigated the thermal stability of HMG1, of the truncated protein A-B (HMG1 without the acidic tail C) and of the isolated domains A and B. In 3 mm sodium acetate buffer, pH 5, the thermal melting of domains A and B are identical (transition temperature tm = 43 degrees C and 41 degrees C, denaturation enthalpies DeltaH = 46 kcal.mol-1). The thermal melting of protein A-B presents two nearly identical transitions (tm = 40 degrees C and 41 degrees C, DeltaH = 44 kcal.mol-1 and 46 kcal.mol-1, respectively). We conclude that the two domains A and B within protein A-B behave as independent domains. The thermal melting of HMG1 is biphasic. The two transitions have a different value of tm (38 degrees C and 55 degrees C) and corresponding values of DeltaH around 40 kcal.mol-1. We conclude that within HMG1, the acidic tail C is interacting with one of the two domains A and B, however, the two domains A and B do not interact with each other. At 37 degrees C, one of the two domains A and B, within HMG1, is partly unfolded, whereas the other which interacts with the acidic tail C, is fully native. The interaction free energy of the acidic tail C is estimated to be in the range of 2.5 kcal.mol-1 based on simulations of the thermograms of HMG1 as a function of the interaction free energy.

The supercoiling sensitivity of a bacterial tRNA promoter parallels its responsiveness to stringent control

In Salmonella typhimurium, expression of the hisR locus, a tRNA operon, decreases upon inhibiting DNA gyrase. Here, the hisR promoter dependence on negative DNA supercoiling was examined in vivo and in vitro. Mutant analysis showed the sequence determinants of this dependence to lie in the region between the -10 box and the transcription start site. As with most promoters subject to stringent control, this portion of the hisR promoter is C-G-rich. Replacing a C/G bp with T/A at position -7 partially relieves the supercoiling response while changing the sequence between -5 and + 1 (-CCCCCG-) for -GTTAA- abolishes the response in vitro and in vivo. The relief of the supercoiling dependence closely correlates with increased promoter susceptibility to melting in vivo and a lesser requirement for initiating nucleotides in the formation of stable initiation complexes in vitro. Studies in isoleucine-starved cells showed that such sequence changes mitigate and abolish the hisR promoter response to stringent control, respectively. The data presented suggest that the hisR promoter's sensitivity to stringent regulation arises from the same physical property that confers supercoiling sensitivity, i.e. resistance to melting. We propose that the stringent control mechanism acts by hampering the ability of RNA polymerase to melt the DNA helix.

Assessment of high-affinity hybridization, RNase H cleavage, and covalent linkage in translation arrest by antisense oligonucleotides

Antisense oligonucleotides (ONs) are designed to hybridize target mRNA in a sequence-specific manner and inhibit gene expression by preventing translation, either by activation of RNase H or steric blockage of the ribosome complex. Second-generation ONs, which possess greater binding affinity for target RNA relative to the isosequential phosphodiester (PO) ONs, have been developed and include, among others, peptide nucleic acids (PNA) and N3' P5' phosphoramidate oligonucleotides (npONs). In the present study, PNA and npON derivatives were targeted to the coding portion of the complementary mRNA of the N protein of the vesicular stomatitis virus (VSV) in order to evaluate their ability to arrest translation in an in vitro rabbit reticulocyte lysate system. High-affinity hybridization of ONs lacking RNase H activity was not sufficient to block translation in this test system. Only antisense ONs acting via an RNase H mechanism or by steric hindrance through covalent attachment (via transplatin modification) to the target mRNA were found to definitively arrest translation in this study.

Interstrand crosslinking reaction in transplatin-modified oligo-2'-O-methyl ribonucleotide-RNA hybrids

In the context of developing an approach to irreversibly and specifically link oligonucleotides to RNA, the purpose of this work was to determine the factors interfering with the rate of the rearrangement of the transplatin 1,3-intrastrand crosslinks into interstrand crosslinks, rearrangement triggered by the formation of a double helix between platinated oligo-2'-O-methyl-ribonucleotides and their complementary strands. The rate of the rearrangement has been studied as a function of the length of the hybrids, the location of the intrastrand crosslinks, the nature of the oligonucleotide backbone, and the nature of the doublet replacing the triplet complementary to the intrastrand crosslinks. The thermal stability of the platinated hybrids has been determined in various salt conditions. The results are discussed in relation to the mechanism of the rearrangement. It is shown that the cellular proteins present weaker nonspecific interactions with single-stranded platinated oligo-2'-O-methyl-nucleotides than with the isosequential oligodeoxyribonucleotides.

HMG1 protein inhibits the translesion synthesis of the major DNA cisplatin adduct by cell extracts

When situated in a fork-like synthetic DNA replication substrate, the 1,2-intrastrand crosslink at the d(GpG) site, the most frequent adduct formed in the reaction between DNA and the anticancer drug cisplatin (cis-diamminedichloroplatinum (II)), is efficiently bypassed by eukaryotic cell extracts. We show here that the rat high-mobility-group protein 1 (HMG1) binds preferentially to the platinated fork-like synthetic DNA and inhibits the translesion synthesis. The same protein, but without the acidic tail, inhibits also the translesion synthesis. These results suggest that HMG proteins might contribute to the sensitivity of cells to cisplatin by directly affecting DNA replication.

Chemical versatility of transplatin monofunctional adducts within multiple site-specifically platinated DNA

The first step of the reaction between DNA and the antitumor drug cisplatin or its clinically inactive isomer transplatin yields monofunctional adducts. Most of the cisplatin monofunctional adducts further react and rather rapidly (t(1/2) smaller than a few hours) to form intrastrand and interstrand cross-links. It is generally accepted that the clinical activity of cisplatin is related to the formation of bifunctional lesions. As concerns transplatin, several studies disagree on the rate of closure of the monofunctional adducts and the nature of the bifunctional lesions. In order to explain these discrepancies, we have prepared several duplexes containing a single monofunctional trans-[Pt(NH3)2(dG)Cl]+ adduct and zero to two monofunctional [Pt(dien)(dG)]2+ adducts at defined positions. In these duplexes, the inert [Pt(dien)(dG)]2+ adducts mimic the presence of transplatin monofunctional adducts. We show that the closure of the transplatin monofunctional adducts is strongly affected by the presence of other adducts and by the length of the duplexes. These findings suggest that the discrepancies in the literature originate from the nature of the platinated samples (molar ratio of bound platinum per nucleotide, length of the DNA fragments). Our general conclusion is that within transplatin-modified DNA, at a low level of platination, the monofunctional adducts evolve slowly (t(1/2) > 24 h) into bifunctional lesions and that these bifunctional lesions are mainly interstrand cross-links. This could explain, at least in part, the clinical inefficiency of transplatin.

Distortions of the DNA double helix induced by 1,3-trans-diamminedichloroplatinum(II)-intrastrand cross-link: an internal coordinate molecular modeling study

A trans-diamminedichloroplatinum(II) (trans-DDP) intrastrand adduct within the sequence d(TCTG*TG*TC).d(GACACAGA) (where G* represents a platinated guanine) is modeled on the basis of qualitative experimental data concerning global unwinding and curvature as well as information on base pairing. Modeling is performed using the internal coordinate JUMNA program, specific to nucleic acids, and modified to include the possibility of covalently bound ligands. Calibration of the energy functions representing the Pt-N7 bond with guanine is described. The platinum atom and the platinum-nitrogen bonds are parameterized for use in the Hückel Del Re method to calculate monopoles at each atom. These monopoles are consistent with the Flex force field included in Jumna. By developing an appropriate minimization protocol we are able to generate stable, distorted three-dimensional structures compatible with the experimental data and including an unusually high global unwinding. No a priori geometric assumptions are made in generating these structures.

Solution structure of the wild-type HMGI a box by 1 h and 15n NMR and molecular modelling

Abstract:

The solution structure of the wild-type A box of rat HMG1 has been determined by heteronuclear three-dimensional NMR and molecular modelling. This structure adopts a "L" shape structure globaly similar to that described for a mutant A box and other HMG boxes. However the wild-type A box contains two Cys residues which could form intramolecular bridge in an oxidative environment. This should be into competition with a contribution of the thiol groups in the binding ofHMG proteins to cisplatin-modified DNA.

Transplatin-modified oligo(2'-O-methyl ribonucleotide)s: a new tool for selective modulation of gene expression

In the reaction between trans-diamminedichloroplatinum(II) and single-stranded oligo(2'-O-methyl ribonucleotide)s containing the sequence GNG (N being a nucleotide residue), the 1,3-trans-{Pt-(NH3)2[GNG]} cross-links are formed. The 1,3-intrastrand cross-links are inert within the single-stranded oligonucleotides. By contrast, they rearrange into interstrand cross-links when the platinated oligonucleotides are paired with their complementary RNA strands. The rate of the interstrand cross-linking reaction depends upon the sequence facing the intrastrand cross-links. When the complementary sequences are 5'-CN'C (N' being a nucleotide), the rates are rather slow (T1/2 >/= 3 h at 37 degrees C). The rearrangement of the intrastrand cross-links into interstrand cross-links can be achieved in a few minutes when the triplets facing the intrastrand cross-links are replaced by doublet 5'-UA or 5'-CA. In vitro, the specificity of the cross-linking reaction between a platinated oligo(2'-O-methyl ribonucleotide) and its target sequence (containing the 5'-CA doublet) located within the coding region of Ha-ras mRNA is demonstrated by steric blocking of reverse transcriptase and translation machinery. Within the HBL100ras1 cells, this platinated oligonucleotide binds specifically and irreversibly to the cognate Ha-ras mRNA. It also inhibits the proliferation of the HBL100ras1 cells in a dose-dependent manner. The fast and specific interstrand cross-linking reaction triggered by the formation of a double helix between platinated oligo(2'-O-methyl ribonucleotide)s and RNA enhances the potential of the oligonucleotides which do not induce mRNA cleavage by RNase H, to modulate gene expression by steric blocking of the translation machinery.

Rearrangement of interstrand cross-links into intrastrand cross-links in cis-diamminedichloroplatinum(II)-modified DNA

In the reaction of the anticancer drug cis-diamminedichloroplatinum(II) (cis-DDP) with DNA, bifunctional intrastrand and interstrand cross-links are formed. In this work, we show that at 37 degrees C interstrand cross-links (ICL) are labile and rearrange into intrastrand cross-links. The ICL instability was first studied with a 10 base pairs (bp) double-stranded oligonucleotide containing a unique site-specific ICL resulting from chelation of the N7 position of two guanine residues on the opposite strands of DNA at the d(GC/GC) site by a cis-diammineplatinum(II) residue. The bonds between the platinum and the N7 of guanine residues within the interstrand adduct are cleaved. In 50 mM NaCl or NaClO4, this cleavage results in the formation of monofunctional adducts which subsequently form intrastrand cross-links. One cleavage reaction takes place per cross-linked duplex in either of both DNA strands. Whereas the starting cross-linked 10 bp duplex is hydrogen bonded, the two complementary DNA strands separate after the cleavage of the ICL. Under these conditions, the cleavage reaction is irreversible allowing its rate measurement (t1/2= 29+/-2 h) and closure of monofunctional adducts to intrastrand cross-links occurs within single-stranded DNA. Within a longer cross-linked oligonucleotide (20 bp), ICL are apparently more stable (t1/2= 120+/-12 h) as a consequense of monofunctional adducts closure back to ICL. We propose that the ICL cleavage is reversible in DNA and that these adducts rearrange finally into intrastrand cross-links. Our results could explain an 'ICL unhooking' in previously reported in vivo repair studies [Zhenet al. (1993)Carcinogenesis14, 919-924].