Risk evaluation of cognitive impairment in patients with heart failure: A call for action.

Background: Cognitive impairment (CI) is common in patients with heart failure (HF) and impacts treatment adherence and other aspects of patient life in HF. Recognition of CI in patients with HF is therefore important. We aimed to develop a risk model with easily available patient characteristics, to identify patients with HF who are at high risk to be cognitively impaired and in need for further cognitive investigation. Methods & results: The risk model was developed in 611 patients ≥ 60 years with HF from the TIME-CHF trial. Fifty-six (9 %) patients had CI (defined as Hodkinson Abbreviated Mental Test ≤ 7). We assessed the association between potential predictors and CI with least-absolute-shrinkage-and-selection-operator (LASSO) regression analysis. The selected predictors were: older age, female sex, NYHA class III or IV, Charlson comorbidity index ≥ 6, anemia, heart rate ≥ 70 bpm and systolic blood pressure ≥ 145 mmHg. A model that combined these variables had a c-statistic of 0.70 (0.63-0.78). The model was validated in 155 patients ≥ 60 years with HF from the ECHO study. In the validation cohort 51 (33 %) patients had CI (defined as a Mini Mental State Exam ≤ 24). External validation showed an AUC of 0.56 (0.46-0.66). Conclusions: This risk model with easily available patient characteristics has poor predictive performance in external validation, which may be due to case-mix variation. These findings underscore the need for active screening and standardized assessment for CI in patients with HF.

Cardiac Structure and Function Is Associated With Hemispatial Neglect Severity.

Background: Hemispatial neglect is a debilitating consequence of right hemispheric ischemic stroke (RIS), with evidence that patient-level factors influence neglect severity. Study objective: Determine if cardiac function is associated with presence and severity of neglect, independent of infarct size. Methods: Two hundred and eighteen non-demented, RIS with cerebral MRI and echocardiography who completed ≥1 of 4 tests evaluating neglect were included. Age- and sex- adjusted Z-scores defined neglect with severity categorized as no neglect, neglect on one or neglect on ≥2 tests. The dependent variable was presence of neglect (multivariable logistic regression), or neglect severity (multinomial logistic regression). The association with left ventricular (LV) structure/function (independent variable) was evaluated using separate nested adjustment models. Results: Patients were on average 61 yo (21-95), female (50%), black (53%), with an ejection fraction of 60% (IQR 20-75%). Fifty eight (27%) had neglect. Each 1 cm increase in LV systolic diameter was associated with a higher relative risk of having neglect on two tests compared to those with no neglect (RRR = 1.83, 95% CI 1.01-3.32), but not after adjusting for education and DWI volume (RRR = 1.68, 95% CI 0.89-3.19). Per 1 cm increase in left atrial (LA) diameter, the relative risk of having neglect on 2 tests vs. no neglect was over two times higher (95% CI 1.04-4.77), but lost significance in the final model (RRR = 1.73, 95% CI 0.76-3.94). Conclusions: We found an association between markers of diastolic dysfunction (enlarging LV, compensatory enlarging LA) and severity of neglect, suggesting that cardiac structure, and function affects not only lesion volume, but also the functional consequences of infarct volume.

Replication studies of carboxymethylated DNA lesions in human cells.

Metabolic activation of some N-nitroso compounds (NOCs), an important class of DNA damaging agents, can induce the carboxymethylation of nucleobases in DNA. Very little was previously known about how the carboxymethylated DNA lesions perturb DNA replication in human cells. Here, we investigated the effects of five carboxymethylated DNA lesions, i.e. O6-CMdG, N6-CMdA, N4-CMdC, N3-CMdT and O4-CMdT on the efficiency and fidelity of DNA replication in HEK293T human embryonic kidney cells. We found that, while neither N6-CMdA nor N4-CMdC blocked DNA replication or induced mutations, N3-CMdT, O4-CMdT and O6-CMdG moderately blocked DNA replication and induced substantial frequencies of T→A (81%), T→C (68%) and G→A (6.4%) mutations, respectively. In addition, our results revealed that CRISPR-Cas9-mediated depletion of Pol η resulted in significant drops in bypass efficiencies of N4-CMdC and N3-CMdT. Diminution in bypass efficiencies was also observed for N6-CMdA and O6-CMdG upon depletion of Pol κ, and for O6-CMdG upon removal of Pol ζ. Together, our study provided molecular-level insights into the impacts of the carboxymethylated DNA lesions on DNA replication in human cells, revealed the roles of individual translesion synthesis DNA polymerases in bypassing these lesions, and suggested the contributions of O6-CMdG, N3-CMdT and O4-CMdT to the mutations found in p53 gene of human gastrointestinal cancers.

Replicative Bypass Studies of α-Anomeric Lesions of 2'-Deoxyribonucleosides in Vitro.

Genomic integrity is constantly challenged by a variety of endogenous and exogenous DNA damaging agents, which can lead to the formation of 104-105 DNA lesions per cell per day. Reactive oxygen species (ROS) represent a major type of DNA damaging agent. Specifically, a hydroxyl radical can attack the C1' position of 2-deoxyribose, and the ensuing carbon-centered radical, if improperly repaired, can cause the inversion of stereochemical configuration at the C1' to give α-anomeric lesions. In this study, we assessed the replicative bypass of α-dA, α-dT, α-dC, and α-dG in template DNA by conducting primer extension assays with the use of purified translesion synthesis DNA polymerases. Our results revealed that human polymerase (Pol) η, but not human Pol κ, Pol ι, or yeast Pol ζ, was capable of bypassing all of the α-dN lesions and extending the primer to generate full-length replication products. Data from steady-state kinetic measurements showed that Pol η was the most efficient in inserting the correct nucleotides opposite the modified nucleosides, with the relative efficiencies of nucleotide incorporation following the order of α-dA > α-dG > α-dT > α-dC. Additionally, human Pol η was found to misincorporate dTMP opposite α-dT and dCMP opposite α-dC at frequencies of 66% and 24%, respectively, whereas α-dA and α-dG were weakly miscoding. These findings provided important knowledge about the effects these α-dN lesions have on the fidelity and efficiency of DNA replication mediated by human Pol η.

Replicative Bypass of O2-Alkylthymidine Lesions in Vitro.

DNA alkylation represents a major type of DNA damage and is generally unavoidable due to ubiquitous exposure to various exogenous and endogenous sources of alkylating agents. Among the alkylated DNA lesions, O2-alkylthymidines (O2-alkyldT) are known to be persistent and poorly repaired in mammalian systems and have been shown to accumulate in the esophagus, lung, and liver tissue of rats treated with tobacco-specific N-nitrosamines, i.e., 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN). In this study, we assessed the replicative bypass of a comprehensive set of O2-alkyldT lesions, with the alkyl group being a Me, Et, nPr, iPr, nBu, iBu, or sBu, in template DNA by conducting primer extension assays with the use of major translesion synthesis DNA polymerases. The results showed that human Pol η and, to a lesser degree, human Pol κ, but not human polymerase ι or yeast polymerase ζ, were capable of bypassing all O2-alkyldT lesions and extending the primer to generate full-length replication products. Data from steady-state kinetic measurements showed that human Pol η exhibited high frequencies of misincorporation of dCMP opposite those O2-alkyldT lesions bearing a longer straight-chain alkyl group. However, the nucleotide misincorporation opposite branched-chain lesions was not selective, with dCMP, dGMP, and dTMP being inserted at similar efficiencies, though the total frequencies of nucleotide misincorporation opposite the branched-chain lesions differed and followed the order of O2-iPrdT > O2-iBudT > O2-sBudT. Together, the results from the present study provided important knowledge about the effects of the length and structure of the alkyl group in the O2-alkyldT lesions on the fidelity and efficiency of DNA replication mediated by human Pol η.

Translesion synthesis of O4-alkylthymidine lesions in human cells.

Environmental exposure, endogenous metabolism and cancer chemotherapy can give rise to alkylation of DNA, and the resulting alkylated thymidine (alkyldT) lesions were found to be poorly repaired and persistent in mammalian tissues. Unrepaired DNA lesions may compromise genomic integrity by inhibiting DNA replication and inducing mutations in these processes. In this study, we explored how eight O4-alkyldT lesions, with the alkyl group being a Me, Et, nPr, iPr, nBu, iBu, (R)-sBu and (S)-sBu, are recognized by DNA replication machinery in HEK293T human embryonic kidney cells. We found that the O4-alkyldT lesions are moderately blocking to DNA replication, with the bypass efficiencies ranging from 20 to 33% in HEK293T cells, and these lesions induced substantial frequencies T→C transition mutation. We also conducted the replication experiments in the isogenic cells where individual translesion synthesis (TLS) DNA polymerases were depleted by the CRISPR/Cas9 genome editing method. Our results showed that deficiency in Pol η or Pol ζ, but not Pol κ or Pol ι, led to pronounced drops in bypass efficiencies for all the O4-alkyldT lesions except O4-MedT. In addition, depletion of Pol ζ resulted in significant decreases in T→C mutation frequencies for all the O4-alkyldT lesions except O4-MedT and O4-nBudT. Thus, our study provided important new knowledge about the cytotoxic and mutagenic properties of the O4-alkyldT lesions and defined the roles of TLS polymerases in bypassing these lesions in human cells.

In Vitro Lesion Bypass Studies of O(4)-Alkylthymidines with Human DNA Polymerase η.

Environmental exposure and endogenous metabolism can give rise to DNA alkylation. Among alkylated nucleosides, O(4)-alkylthymidine (O(4)-alkyldT) lesions are poorly repaired in mammalian systems and may compromise the efficiency and fidelity of cellular DNA replication. To cope with replication-stalling DNA lesions, cells are equipped with translesion synthesis DNA polymerases that are capable of bypassing various DNA lesions. In this study, we assessed human DNA polymerase η (Pol η)-mediated bypass of various O(4)-alkyldT lesions, with the alkyl group being Me, Et, nPr, iPr, nBu, iBu, (R)-sBu, or (S)-sBu, in template DNA by conducting primer extension and steady-state kinetic assays. Our primer extension assay results revealed that human Pol η, but not human polymerases κ and ι or yeast polymerase ζ, was capable of bypassing all O(4)-alkyldT lesions and extending the primer to generate full-length replication products. Data from steady-state kinetic measurements showed that Pol η preferentially misincorporated dGMP opposite O(4)-alkyldT lesions with a straight-chain alkyl group. The nucleotide misincorporation opposite most lesions with a branched-chain alkyl group was, however, not selective, where dCMP, dGMP, and dTMP were inserted at similar efficiencies opposite O(4)-iPrdT, O(4)-iBudT, and O(4)-(R)-sBudT. These results provide important knowledge about the effects of the length and structure of the alkyl group in O(4)-alkyldT lesions on the fidelity and efficiency of DNA replication mediated by human Pol η.

Exercise, but not acute sleep loss, increases salivary antimicrobial protein secretion.

Sleep deficiencies may play a role in depressing immune parameters. Little is known about the impact of exercise after sleep deprivation on mucosal immunity. The purpose of this study was to quantify salivary antimicrobial proteins (AMPs) in response to sleep loss before and after exercise. Four men and 4 women (age: 22.8 ± 2; : 49.1 ± 7.1 ml · kg(-1) · min(-1)) completed 2 exercise trials consisting of 45 minutes of running at 75% VO2peak after a normal night of sleep (CON) and after a night without sleep (WS). Exercise trials were separated by 10 ± 3 days. Saliva was collected before, immediately after, and 1 hour after exercise. LL-37, HNP1-3, Lactoferrin (Lac), and Lysozyme (Lys) were measured. Sleep loss did not affect the concentration or secretion rate of AMPs before or in response to exercise. However, exercise increased the concentration from pre- to post-exercise of LL-37 (pre: 15.5 ± 8.7; post: 22.3 ± 16.2 ng · ml(-1)), HNP1-3 (pre: 2.2 ± 2.3; post: 3.3 ± 2.5 µg · ml(-1)), Lac (pre: 5,234 ± 4,202; post: 12,283 ± 10,995 ng · ml(-1)), and Lys (pre: 5,831 ± 4,465; post: 12,542 ± 10,755 ng · ml(-1)), p <= 0.05. The secretion rates were higher immediately after and 1 hour after exercise compared with before exercise for LL-37 (pre: 3.1 ± 2.1; post: 5.1 ± 3.7; +1: 6.9 ± 8.4 ng · min(-1)), HNP1-3 (pre: 0.38 ± 0.38; post: 0.80 ± 0.75; +1: 0.84 ± 0.67 µg · min(-1)), Lac (pre: 1,096 ± 829; post: 2,948 ± 2,923; +1: 2,464 ± 3,785 ng · min(-1)), and Lys (pre: 1,534 ± 1,790; post: 3,042 ± 2,773; +1: 1,916 ± 1,682 ng · min-(1)), p <= 0.05. These data suggest that the major constituents of the mucosal immune system are unaffected by acute sleep loss and by exercise after acute sleep loss. Exercise increased the concentration and secretion rate of each AMP suggesting enhanced immunity and control of inflammation, despite limited sleep.