Epidemiology and impact of frailty in patients with atrial fibrillation in Europe

BACKGROUND

Frailty is a medical syndrome characterised by reduced physiological reserve and increased vulnerability to stressors. Data regarding the relationship between frailty and atrial fibrillation (AF) are still inconsistent.

OBJECTIVES

We aim to perform a comprehensive evaluation of frailty in a large European cohort of AF patients.

METHODS

A 40-item frailty index (FI) was built according to the accumulation of deficits model in the AF patients enrolled in the ESC-EHRA EORP-AF General Long-Term Registry. Association of baseline characteristics, clinical management, quality of life, healthcare resources use and risk of outcomes with frailty was examined.

RESULTS

Among 10,177 patients [mean age (standard deviation) 69.0 (11.4) years, 4,103 (40.3%) females], 6,066 (59.6%) were pre-frail and 2,172 (21.3%) were frail, whereas only 1,939 (19.1%) were considered robust. Baseline thromboembolic and bleeding risks were independently associated with increasing FI. Frail patients with AF were less likely to be treated with oral anticoagulants (OACs) (odds ratio 0.70, 95% confidence interval 0.55-0.89), especially with non-vitamin K antagonist OACs and managed with a rhythm control strategy, compared with robust patients. Increasing frailty was associated with a higher risk for all outcomes examined, with a non-linear exponential relationship. The use of OAC was associated with a lower risk of outcomes, except in patients with very/extremely high frailty.

CONCLUSIONS

In this large cohort of AF patients, there was a high burden of frailty, influencing clinical management and risk of adverse outcomes. The clinical benefit of OAC is maintained in patients with high frailty, but not in very high/extremely frail ones.

Multiple doses of diacylglycerol and calcium ionophore are necessary to activate AP-1 enhancer activity and induce markers of macrophage differentiation

In contrast to phorbol esters, multiple doses of diacylgycerols are needed to differentiate U937 human monoblastic leukemic cells to a macrophage-like phenotype. Although both of these agents similarly activate protein kinase C in vitro, it is not known why these agents appear to have differing biologic effects. One possibility is that they regulate gene transcription in slightly different ways. Regulation of gene transcription by phorbol esters is complex and involves the stimulation of the transactivating proteins Jun and Fos which form dimers and bind to the AP-1 enhancer elements (5'-TGAGTCA-3'). To understand whether diacylglycerols regulate gene transcription similarly to phorbol esters and to examine whether activation of AP-1 enhancer activity is correlated with differentiation, we have treated U937 human monoblastic leukemic cells with these agents and examined activation of transcription from AP-1 enhancer elements. We find that, although a single dose of diacylglycerol, like phorbol esters, is sufficient to elevate mRNA levels of both the c-jun and c-fos protooncogenes, in contrast to phorbol esters there is no increase in either Jun protein or activation of AP-1 enhancer activity. However, multiple doses of this agent given over 24 h stimulate repeated elevations in c-jun and c-fos mRNA, increases in Jun protein, and enhancer activation. Treatment of U937 cells with ionomycin, a calcium ionophore, also stimulates an increase in c-jun mRNA, but neither activates AP-1 enhancer activity nor stimulates differentiation of these cells. However ionomycin functions to enhance the effects of diacylglycerols both on transcriptional activation and U937 differentiation. These results suggest a complex regulation of AP-1 enhancer activity in U937 cells by diacylglycerols involving both transcriptional and post-transcriptional regulatory mechanisms. Maximal activation of AP-1 enhancer elements, and not changes in jun and fos mRNA, is correlated with increases in markers of U937 differentiation. These changes may be important in the early events leading to differentiation of hematopoietic cells.

Lack of phosphorylation of lipocortin I in A431 epidermoid carcinoma cells treated with phorbol esters

To examine in vivo phosphorylation of lipocortin I we made use of a polyclonal antibody to an amino terminal peptide of lipocortin I. This antibody does not recognize any other member of the annexin protein family, and can both immunoprecipitate lipocortin I and recognize this protein on western blots. Using cleaved forms of lipocortin I, we have been able to demonstrate that protein kinase C phosphorylates this protein in vitro within the first 29 amino terminal amino acids. However, the addition of phorbol esters to A431 cells over a wide range of concentrations and for varying periods of time did not stimulate the phosphorylation of this protein. Since in vitro lipocortin I is an excellent substrate for all three isoforms, alpha, beta, gamma, of protein kinase C, the discrepancy in these findings is not secondary to the presence of varying forms of this protein kinase within different cell types.

Varied differentiation responses of human leukemias to bryostatin 1

Bryostatin 1, a macrocyclic lactone isolated from a marine bryozoan, has significant antineoplastic activity against the murine cell line P388. Like phorbol esters, bryostatin 1 is capable of binding to and activating protein kinase C, but these two compounds differ in the ability of bryostatin 1 to act as a tumor promoter. We have investigated whether bryostatin 1 can modulate the differentiated phenotype of fresh samples of human myeloid leukemia. We find that six of seven samples responded to bryostatin treatment with changes associated with a more differentiated phenotype including increases in macrophage-like morphology and an increase in adherence and OKM1 and alpha-naphthyl acetate esterase activity positivity. The percentage of cells within each sample evidencing these changes varied markedly among the seven patients' cells examined. Because of the effects of bryostatin on fresh samples we examined the ability of bryostatin to differentiate four HL-60 cell sublines obtained from different laboratories. We found that two of the cell lines did not respond either with an inhibition of growth or morphological change, while one was inhibited, and one showed both growth inhibition and some induction of macrophage-like morphology when treated with bryostatin. To test whether other differentiating agents would enhance the effects of bryostatin 1, we added tumor necrosis factor alpha and bryostatin to these four cell lines. The addition of both agents effected an additive inhibition of growth. These data suggest that bryostatin 1 alone or in combination with other biological response modifiers may have a role in the treatment of human leukemia.

Differentiation of HL-60 cells is associated with an increase in the 35-kDa protein lipocortin I

Lipocortin I, a 35-kDa protein, has been detected in terminally differentiated monocytes and neutrophils. This calcium-phospholipid binding protein appears to be identical to a 35-kDa protein that can serve as a substrate for the EGF-receptor/tyrosine kinase. We have used the human myelocytic cell line HL-60 to explore whether differentiation of hematopoietic cells is associated with changes in the level of lipocortin I. We find that differentiation of HL-60 cells toward the macrophage lineage by the addition of phorbol esters or vitamin D3 or toward neutrophils with dibutyryl cyclic AMP or dimethyl sulfoxide is accompanied by an increase in the cellular content of lipocortin I. In comparison, treatment of HL-60 cells with bryostatin 1, a compound that activates protein kinase C but does not differentiate HL-60 cells, did not effect the level of 35 kDa protein. We have developed a radioimmunoassay to quantitate this protein by using a polyclonal antibody to a synthetic amino terminal peptide of the 35-kDa protein. This antibody recognizes purified pig lung 35-kDa protein as well as a single 35-kDa protein in HL-60 and A-431 cells as determined by Western blotting and immune precipitation. Differentiated HL-60 cells contain 2.6-fold the amount of 35-kDa protein found in undifferentiated HL-60 cells. Our findings that the addition of phorbol esters to HL-60 cells results in an increase in the mRNA for the 35-kDa protein and in an increase in the incorporation of 35S-methionine into the protein suggest that transcriptional activation or increased stability of the mRNA is responsible for the increased rate of synthesis and accumulation of lipocortin I during differentiation of these cells. In the absence of added divalent cations, we have determined that in differentiated HL-60 cells 79% of lipocortin I protein is located in the cytosol while 21% of the total cellular protein is bound to the particulate fraction. The 35-kDa protein can be removed from the particulate fraction by incubation with chelators or treatment with phospholipase A2 or phospholipase C. Addition of the calcium ionophore A23187 to intact differentiated HL-60 cells causes the 35-kDa protein to associate with the particulate fraction of the cell, suggesting that modulation of intracellular calcium levels may play a role in changing the intracellular location of this protein.