Histological validation of atrial structural remodelling in patients with atrial fibrillation.

BACKGROUND AND AIMS: This study aimed to histologically validate atrial structural remodelling associated with atrial fibrillation. METHODS AND RESULTS: Patients undergoing atrial fibrillation ablation and endomyocardial atrial biopsy were included (n = 230; 67 ± 12 years old; 69 women). Electroanatomic mapping was performed during right atrial pacing. Voltage at the biopsy site (Vbiopsy), global left atrial voltage (VGLA), and the proportion of points with fractionated electrograms defined as ≥5 deflections in each electrogram (%Fractionated EGM) were evaluated. SCZtotal was calculated as the total width of slow conduction zones, defined as regions with a conduction velocity of <30 cm/s. Histological factors potentially associated with electroanatomic characteristics were evaluated using multiple linear regression analyses. Ultrastructural features and immune cell infiltration were evaluated by electron microscopy and immunohistochemical staining in 33 and 60 patients, respectively. Fibrosis, intercellular space, myofibrillar loss, and myocardial nuclear density were significantly associated with Vbiopsy (P = .014, P < .001, P < .001, and P = .002, respectively) and VGLA (P = .010, P < .001, P = .001, and P < .001, respectively). The intercellular space was associated with the %Fractionated EGM (P = .001). Fibrosis, intercellular space, and myofibrillar loss were associated with SCZtotal (P = .028, P < .001, and P = .015, respectively). Electron microscopy confirmed plasma components and immature collagen fibrils in the increased intercellular space and myofilament lysis in cardiomyocytes, depending on myofibrillar loss. Among the histological factors, the severity of myofibrillar loss was associated with an increase in macrophage infiltration. CONCLUSION: Histological correlates of atrial structural remodelling were fibrosis, increased intercellular space, myofibrillar loss, and decreased nuclear density. Each histological component was defined using electron microscopy and immunohistochemistry studies.

Atrial Structural Remodeling in Patients With Atrial Fibrillation Is a Diffuse Fibrotic Process: Evidence From High-Density Voltage Mapping and Atrial Biopsy.

Background Low-voltage areas (LVAs) in the atria of patients with atrial fibrillation are considered local fibrosis. We hypothesized that voltage reduction in the atria is a diffuse process associated with fibrosis and that the presence of LVAs reflects a global voltage reduction. Methods and Results We examined 140 patients with atrial fibrillation and 13 patients with a left accessory pathway (controls). High-density bipolar voltage mapping was performed using a grid-mapping catheter during high right atrial pacing. Global left atrial (LA) voltage (VGLA) in the whole LA and regional LA voltage (VRLA) in 6 anatomic regions were evaluated with the mean of the highest voltage at a sampling density of 1 cm2. Patients with atrial fibrillation were categorized into quartiles by VGLA. LVAs were evaluated at voltage cutoffs of 0.1, 0.5, 1.0, and 1.5 mV. Twenty-eight patients with atrial fibrillation also underwent right atrial septum biopsy, and the fibrosis extent was quantified. Voltage at the biopsy site (Vbiopsy) was recorded. VGLA results by category were Q1 (<4.2 mV), Q2 (4.2-5.6 mV), Q3 (5.7-7.0 mV), and Q4 (≥7.1 mV). VRLA at any region was reduced as VGLA decreased. VGLA and VRLA did not differ between Q4 and controls. The presence of LVAs increased as VGLA decreased at any voltage cutoff. Biopsies revealed 11±6% fibrosis, which was inversely correlated with both Vbiopsy and VGLA (r=-0.71 and -0.72, respectively). Vbiopsy was correlated with VGLA (r=0.82). Conclusions Voltage reduction in the LA is a diffuse process associated with fibrosis. Presence of LVAs reflects diffuse voltage reduction of the LA.

Impact of Renal Dysfunction on Left Atrial Structural Remodeling and Recurrence After Catheter Ablation for Atrial Fibrillation　- A Propensity Score Matching Analysis.

BACKGROUND: Renal dysfunction coexists with other known risk factors of left atrial (LA) structural remodeling, expressed as low-voltage zones (LVZs), and the recurrence of atrial fibrillation (AF) after ablation. This study aimed to determine whether renal dysfunction had an independent effect on the presence of LVZs and recurrence after AF ablation, using propensity score (PS) matching analysis.Methods and Results:448 consecutive patients who underwent their initial AF ablation were enrolled. Chronic kidney disease (CKD) was defined as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2, with 126 (28%) patients having CKD. Using PS matching analysis, new subsets (CKD and non-CKD group, n=103 each) were obtained, matched for age, sex, AF type, and LA volume. The presence of LVZs defined as bipolar voltage <0.5 mV was higher in the CKD group than in the non-CKD group (31% vs. 17%, P=0.034). Multivariate analysis showed eGFR was an independent predictor of the presence of LVZs (odds ratio 1.31 per 10-mL/min/1.73 m2decrease, P=0.029). AF-free survival rate was significantly lower in the CKD patients during 20±9 months of follow-up (63% vs. 82%, P=0.019), and eGFR was shown to be an independent predictor of recurrence (hazard ratio 1.29 per 10-mL/min/1.73 m2decrease, P=0.006), but the presence of LVZs did not predict recurrence. CONCLUSIONS: Renal dysfunction independently predicted not only the recurrence of AF after ablation but also the presence of LVZs.

Paclitaxel-induced HMGB1 release from macrophages and its implication for peripheral neuropathy in mice: Evidence for a neuroimmune crosstalk.

Given our recent evidence for the role of high mobility group box 1 (HMGB1) in chemotherapy-induced peripheral neuropathy (CIPN) in rats, we examined the origin of HMGB1 and the upstream and downstream mechanisms of HMGB1 release involved in paclitaxel-induced neuropathy in mice. Paclitaxel treatment developed mechanical allodynia in mice, as assessed by von Frey test, which was prevented by an anti-HMGB1-neutralizing antibody or thrombomodulin alfa capable of inactivating HMGB1. RAGE or CXCR4 antagonists, ethyl pyruvate or minocycline, known to inhibit HMGB1 release from macrophages, and liposomal clodronate, a macrophage depletor, prevented the paclitaxel-induced allodynia. Paclitaxel caused upregulation of RAGE and CXCR4 in the dorsal root ganglia and macrophage accumulation in the sciatic nerve. In macrophage-like RAW264.7 cells, paclitaxel evoked cytoplasmic translocation of nuclear HMGB1 followed by its extracellular release, and overexpression of CBP and PCAF, histone acetyltransferases (HATs), known to cause acetylation and cytoplasmic translocation of HMGB1, which were suppressed by ethyl pyruvate, N-acetyl-l-cysteine, an anti-oxidant, and SB203580 and PDTC, inhibitors of p38 MAP kinase (p38MAPK) and NF-κB, respectively. Paclitaxel increased accumulation of reactive oxygen species (ROS) and phosphorylation of p38MAPK, NF-κB p65 and I-κB in RAW264.7 cells. In mice, N-acetyl-l-cysteine or PDTC prevented the paclitaxel-induced allodynia. Co-culture of neuron-like NG108-15 cells or stimulation with their conditioned medium promoted paclitaxel-induced HMGB1 release from RAW264.7 cells. Our data indicate that HMGB1 released from macrophages through the ROS/p38MAPK/NF-κB/HAT pathway participates in the paclitaxel-induced peripheral neuropathy in mice, and unveils an emerging therapeutic avenue targeting a neuroimmune crosstalk in CIPN.

Radioprotective activity of blackcurrant extract evaluated by in vitro micronucleus and gene mutation assays in TK6 human lymphoblastoid cells.

INTRODUCTION: Blackcurrant (Ribs nigrum L.) is a classical fruit that has long been used to prepare juice, jam, liqueur, and sometimes medicines in Europe. Previously, we reported a genome defense effect by the antioxidative activity of several types of blackcurrant extracts (BCEs) in yeast and human cell gene mutation assays. In this study, we determined if BCE exerted radioprotective activity against DNA damage, chromosomal aberration, and gene mutations in the TK6 human lymphoblastoid cell line. We prepared aqueous BCE extracted from mature fruits cultivated in the Aomori Prefecture, Japan. FINDINGS: In the micronucleus test and TK gene mutation assay, TK6 cells were irradiated with 0, 0.125, 0.250, 0.500, and 1.000 Gy with or without 1.0 mg/mL BCE. Intracellular hydrogen peroxide (H2O2) was measured using the fluorescent probe BES-H2O2-Ac. Induction of micronuclei and gene mutations by γ-irradiation exposure was suppressed in combination with BCE. In addition, BCE reduced intracellular H2O2 levels caused by γ-irradiation. CONCLUSIONS: Our findings clearly support the genome defense potential of blackcurrant against γ-induced DNA damage. We postulate that these genome defense activities are related to the antioxidant compounds in blackcurrant.

Protective effects of raw and cooked blackcurrant extract on DNA damage induced by hydrogen peroxide in human lymphoblastoid cells.

CONTEXT: Blackcurrant (Ribes nigrum L.) is a classical fruit that has long been used to make juice, liqueur and sometimes medicines in Europe. The beneficial effects of blackcurrant, which are inhibition of lipopolysaccharide-stimulated inflammatory, anticarcinogenesis and other health effects, have been reported. OBJECTIVE: Previously, we reported the antimutagenic activities of blackcurrant using a yeast gene mutation assay. In this study, we investigated whether this antimutagenicity of blackcurrant was confirmed in human cells. MATERIALS AND METHODS: We prepared four types of aqueous blackcurrant extracts (BCE) from mature and premature with or without heat treatment by microwave. Antioxidant activities of BCE were measured by the DPPH radical scavenger assay. In the DPPH radical scavenger assay, the maximum concentration of BCE was 1.6 mg/reaction. We investigated the antigenotoxic activities of BCE by the comet assay and micronucleus test using the human lymphoblastoid cell line TK6. In the comet assay, TK6 was treated with 300 µM H2O2 without or with BCE at concentrations of 0.5, 1.0, 2.0 and 3.0 mg/mL. In the micronucleus test, TK6 was treated with 1 mg/mL BCE without or with H2O2. RESULTS: All BCEs exhibited more than 90% of inhibition rates of DPPH radicals at the maximum concentration of BCE. DNA damage and micronuclei induced by H2O2 significantly decreased in the each BCE-treated condition. CONCLUSION: The results suggest that BCE treatment can reduce the genomic instability induced by H2O2 in human cells. We consider that these antigenotoxic effects are related to polyphenols, l-ascorbic acid and other antioxidant compounds.