Splenectomy exacerbates atrial inflammatory fibrosis and vulnerability to atrial fibrillation induced by pressure overload in rats: Possible role of spleen-derived interleukin-10

Quantitative histologic assessment of atrial fibrillation-associated fibrosis in animal models: A systematic review

Atrial fibrillation (AF) is the most common sustained arrhythmia, and cardiac fibrosis is a major component in driving its progressive nature. Quantitative histologic assessment of fibrosis in animal models is crucial for understanding AF, but current published studies present various methodologies that limit comparison. This systematic review examines 195 AF studies across multiple animal models (mice, rats, goats, dogs, pigs, and horses) to summarize (1) quantified fibrosis results and (2) methodologies for histologic fibrosis assessment; and (3) evaluate antifibrotic therapies used in these studies. The fibrosis quantified across the studies ranged from 0.34%-60.2% depending on the animal, intervention model, and quantification method. The findings underscore the need for a standardized fibrosis quantification protocol in AF research, enabling comparison across studies and offering greater insight into potential pharmacologic interventions.

Treatments affecting splenic function as a risk factor for valvular heart disease in Childhood Cancer Survivors: A DCCSS-LATER study

PURPOSE

Splenectomy might be a risk factor for valvular heart disease (VHD) in adult Hodgkin lymphoma survivors. As this risk is still unclear for childhood cancer survivors (CCS), the aim of this study is to evaluate the association between treatments affecting splenic function (splenectomy and radiotherapy involving the spleen) and VHD in CCS.

METHODS

CCS were enrolled from the DCCSS-LATER cohort, consisting of 6,165 five-year CCS diagnosed between 1963 and 2002. Symptomatic VHD, defined as symptoms combined with a diagnostic test indicating VHD, was assessed from questionnaires and validated using medical records. Differences in the cumulative incidence of VHD between CCS who received treatments affecting splenic function and CCS who did not were assessed using the Gray test. Risk factors were analyzed in a multivariable Cox proportional hazards model.

RESULTS

The study population consisted of 5,286 CCS, with a median follow-up of 22 years (5-50 years), of whom 59 (1.1%) had a splenectomy and 489 (9.2%) radiotherapy involving the spleen. VHD was present in 21 CCS (0.4%). The cumulative incidence of VHD at the age of 40 years was significantly higher in CCS who received treatments affecting splenic function (2.7%, 95% confidence interval (CI) 0.4%-4.9%) compared with CCS without (0.4%, 95% CI 0.1%-0.7%) (Gray's test, p = 0.003). Splenectomy was significantly associated with VHD in a multivariable analysis (hazard ratio 8.6, 95% CI 3.1-24.1).

CONCLUSIONS AND IMPLICATIONS

Splenectomy was associated with VHD. Future research is needed to determine if CCS who had a splenectomy as part of cancer treatment might benefit from screening for VHD.

Risk factors associated with atrial fibrillation following lung cancer surgery: A multi-center case-control study

BACKGROUND

Postoperative atrial fibrillation (POAF) is a common complication after major thoracic operations. The objective of this case-control study was to identify the risk factors for POAF following lung cancer surgery.

METHODS

In total, 216 patients with lung cancer who were selected from three different hospitals were followed up between May 2020 and May 2022. They were divided into two groups: case group, patients with POAF and control group, patients without POAF (case-control). Risk factors associated with POAF were investigated using univariate and multivariate logistic regression analyses.

RESULTS

Risk factors that were significantly associated with POAF were preoperative brain-type natriuretic peptide (BNP) levels [odds ratio (OR): 4.46; 95% confidence interval (CI): 1.52-13.06; P = 0.0064], sex (OR: 0.07; 95%CI: 0.02-0.28; P = 0.0001), preoperative white blood cell (WBC) count (OR: 3.00; 95%CI: 1.89-4.77; P < 0.0001), lymph node dissection (OR: 11.49; 95%CI: 2.81-47.01; P = 0.0007), and cardiovascular disease (OR: 4.93; 95%CI: 1.14-21.31; P = 0.0326).

CONCLUSION

In summary, data from the three hospitals suggested that preoperative BNP levels, sex, preoperative WBC count, lymph node dissection, and hypertension/coronary heart disease/myocardial infarction were associated with a significantly high risk of POAF following lung cancer surgery.

Immune remodeling and atrial fibrillation

Atrial fibrillation (AF) is a highly prevalent arrhythmia that causes high morbidity and mortality. However, the underlying mechanism of AF has not been fully elucidated. Recent research has suggested that, during AF, the immune system changes considerably and interacts with the environment and cells involved in the initiation and maintenance of AF. This may provide a new direction for research and therapeutic strategies for AF. In this review, we elaborate the concept of immune remodeling based on available data in AF. Then, we highlight the complex relationships between immune remodeling and atrial electrical, structural and neural remodeling while also pointing out some research gaps in these field. Finally, we discuss several potential immunomodulatory treatments for AF. Although the heterogeneity of existing evidence makes it ambiguous to extrapolate immunomodulatory treatments for AF into the clinical practice, immune remodeling is still an evolving concept in AF pathophysiology and further studies within this field are likely to provide effective therapies for AF.

Effects of canagliflozin on human myocardial redox signalling: clinical implications

AIMS

Recent clinical trials indicate that sodium-glucose cotransporter 2 (SGLT2) inhibitors improve cardiovascular outcomes in heart failure patients, but the underlying mechanisms remain unknown. We explored the direct effects of canagliflozin, an SGLT2 inhibitor with mild SGLT1 inhibitory effects, on myocardial redox signalling in humans.

METHODS AND RESULTS

Study 1 included 364 patients undergoing cardiac surgery. Right atrial appendage biopsies were harvested to quantify superoxide (O2.-) sources and the expression of inflammation, fibrosis, and myocardial stretch genes. In Study 2, atrial tissue from 51 patients was used ex vivo to study the direct effects of canagliflozin on NADPH oxidase activity and nitric oxide synthase (NOS) uncoupling. Differentiated H9C2 and primary human cardiomyocytes (hCM) were used to further characterize the underlying mechanisms (Study 3). SGLT1 was abundantly expressed in human atrial tissue and hCM, contrary to SGLT2. Myocardial SGLT1 expression was positively associated with O2.- production and pro-fibrotic, pro-inflammatory, and wall stretch gene expression. Canagliflozin reduced NADPH oxidase activity via AMP kinase (AMPK)/Rac1signalling and improved NOS coupling via increased tetrahydrobiopterin bioavailability ex vivo and in vitro. These were attenuated by knocking down SGLT1 in hCM. Canagliflozin had striking ex vivo transcriptomic effects on myocardial redox signalling, suppressing apoptotic and inflammatory pathways in hCM.

CONCLUSIONS

We demonstrate for the first time that canagliflozin suppresses myocardial NADPH oxidase activity and improves NOS coupling via SGLT1/AMPK/Rac1 signalling, leading to global anti-inflammatory and anti-apoptotic effects in the human myocardium. These findings reveal a novel mechanism contributing to the beneficial cardiac effects of canagliflozin.

Ferroportin-mediated ferroptosis involved in new-onset atrial fibrillation with LPS-induced endotoxemia

Sepsis is a known risk factor for new-onset atrial fibrillation (AF), and previous studies have demonstrated that ferroptosis participates in sepsis-induced organ injury development. Nevertheless, the role of ferroptosis in new-onset AF with sepsis remains largely unknown. This study aims to investigate the underlying mechanisms linking ferroptosis and AF caused by sepsis. LPS-induced endotoxemia is often used to model the acute inflammatory response associated with sepsis. Herein, we reported that ferroptosis was significantly activated in LPS-induced endotoxemia rat model. We also observed that ferroportin (Fpn), the only identified mammalian non-heme iron exporter, was downregulated in the atrium of endotoxemia model. Vulnerability to AF was also significantly increased in a endotoxemia rat model. Additionally, Fpn knockdown by shFpn further increased intracellular iron concentration and oxidative stress and exaggerated the AF vulnerability, which was alleviated by ferroptosis inhibition. Mechanistically, silencing Fpn worsened the alterations in calcium handling proteins expression in a endotoxemia rat model. These findings suggest that Fpn-mediated ferroptosis is involved in the new-onset AF with LPS-induced endotoxemia via worsening the calcium handling proteins dysregulation and provides a novel and promising strategy for preventing AF development in sepsis.

Postoperative atrial fibrillation in pneumonectomy for primary lung cancer

Background

This study assessed the incidence and risk factors (RFs) of postoperative atrial fibrillation (POAF) and its impact on clinical outcomes in patients undergoing pneumonectomy for lung cancer.

Methods

Between 2013 and 2018, this monocentric retrospective study enrolled 324 consecutive pneumonectomy patients for primary lung cancer from our institution and 350 lobectomy and 349 segmentectomy cases matched by age, sex and body mass index (BMI). RF for POAF and postoperative death in pneumonectomy patients were assessed by logistic regression, and long-term outcomes after a median follow-up of 30 (range, 2–61) months by Cox proportional hazard model. Electrophysiology study (EPS) files of 30 AF patients with lung resection history were reviewed.

Results

POAF developed more often after pneumonectomy than lobectomy and segmentectomy (23.2% vs. 6.6% vs. 1.4%, respectively; P<0.001). Among 75 pneumonectomy patients with POAF, POAF was solitary in 55 patients (73.3%) and concurrent with other complications in 3 patients (4%). POAF risk after pneumonectomy was 4 and 22 times that after lobectomy and segmentectomy, respectively, with age >60 years and left atrial diameter (LAd) ≥35 mm as independent predictors. POAF, infection and hemorrhage were independent RFs for perioperative death after pneumonectomy; however, POAF was not RF for long-term death. Pulmonary vein (PV) trigger was identified in 60% (18/30) of AF patients with lung resection history, with stump PVs being more active than non-stump PVs (38.2% vs. 10.5%, P<0.001).

Conclusions

Post-pneumonectomy AF, with remarkable incidence, risk and independent predictors including age >60 years and LAd ≥35 mm, was mostly solitary and possibly secondary to stump and non-stump PV triggers. POAF, along with infection and hemorrhage, was a RF for perioperative death.

Baroreflex Sensitivity in Patients With Atrial Fibrillation

Background

It has been reported that atrial fibrillation (AF) may contribute to impairment of baroreflex sensitivity (BRS). However, the difference of BRS between patients with persistent AF (PeAF) and those with paroxysmal AF (PAF) is unknown. We tested the hypothesis that patients with PeAF have a more impaired BRS compared with those with PAF.

Methods and Results

From October 2015 onwards, a total of 67 patients (14 women [20.9%]; mean age 65.2±10.1 years) with PAF (n=46, 68.7%) and PeAF (n=21, 31.3%), who underwent catheter ablation, were prospectively enrolled. The baseline BRS was evaluated during sinus rhythm. The baseline BRS in patients with PeAF was significantly lower than those with PAF (2.97 [0.52–6.62] ms/mm Hg versus 4.70 [2.36–8.37] ms/mm Hg, P=0.047). The BRS was significantly depressed after catheter ablation in all the patients (4.66 [1.80–7.37] ms/mm Hg versus 0.55 [−0.15 to 1.22] ms/mm Hg, P<0.001). However, the depression of BRS because of catheter ablation appeared attenuated in patients with PeAF when compared with those with PAF. The number of patients who did not show depression of BRS was significantly greater, that is, patients with PeAF (3/12, 25%) than those with PAF (0/46, 0%, P<0.01).

Conclusions

Our findings demonstrated that the baseline BRS was more depressed in patients with PeAF compared with PAF. Catheter ablation depressed BRS irrespective of the type of AF, with a greater effect in patients with PAF than PeAF.

Fulminant myocarditis and atrial fibrillation in child with acute COVID-19

COVID-19 has manifested with ventricular dysfunction and cardiac arrhythmias, most commonly atrial fibrillation (AFib), in adults. However, very few pediatric patients with acute COVID-19 have had cardiac involvement. AFib, an exceedingly rare arrhythmia in otherwise healthy children, has not been reported in children with COVID-19. We report a 15 year-old girl with acute COVID-19, fulminant myocarditis and AFib.

Inflammatory responses mediate brain-heart interaction after ischemic stroke in adult mice

Stroke induces cardiac dysfunction which increases post stroke mortality and morbidity particularly in aging population. Here, we investigated the effects of inflammatory responses as underlying mediators of cardiac dysfunction after stroke in adult mice. Adult (eight-to-nine months) male C57BL/6 mice were subjected to photothrombotic stroke. To test whether immunoresponse to stroke leads to cardiac dysfunction, splenectomy was performed with stroke. Immunohistochemistry, flow cytometry, PCR, ELISA and echocardiography were performed. We found marginal cardiac dysfunction at acute phase and significant cardiac dysfunction at chronic phase of stroke as indicated by significant decrease of left ventricular ejection fraction (LVEF) and shortening fraction (LVSF). Stroke significantly increases macrophage infiltration into the heart and increases IL-1β, IL-6, MCP-1, TGF-β and macrophage-associated inflammatory cytokine levels in the heart as well as induces cardiac-fibrosis and hypertrophy. Splenectomy with stroke significantly reduces macrophage infiltration into heart, decreases inflammatory factor expression in the heart, decreases cardiac hypertrophy and fibrosis, as well as significantly improves cardiac function compared to non-splenectomized adult stroke mice. Therefore, cerebral ischemic stroke in adult mice induces chronic cardiac dysfunction and secondary immune response may contribute to post stroke cardiac dysfunction.

M2b Macrophages Regulate Cardiac Fibroblast Activation and Alleviate Cardiac Fibrosis After Reperfusion Injury

BACKGROUND

Macrophages play an important role in the development of cardiac fibrosis. However, the roles of different macrophage subtypes in cardiac fibroblast (CF) activation and cardiac fibrosis are unknown.

METHODS AND RESULTS

Bone marrow-derived macrophages (BMDMs) were treated with different stimuli to induce differentiation into M1, M2a, M2b, and M2c macrophage subtypes. CFs were co-cultured with different subtypes of macrophages or cultured with macrophage supernatants. Results revealed that M2b macrophages significantly suppressed the proliferation and migration of CFs, the expression of fibrosis-related proteins (collagen I [COL-1] and α-smooth muscle actin [α-SMA]), and differentiation into cardiac myofibroblasts (MFs). The opposite effects were observed with M2a macrophages. A rat model of cardiac ischemia/reperfusion (I/R) injury was used to determine the effect of M2b macrophages transplantation. After cardiac I/R injury, transplantation of M2b macrophages improved cardiac function and reduced cardiac fibrosis. The effect of macrophage subtypes on p-ERK, ERK, p-p38, and p38 phosphorylation was examined by Western blotting. The results showed that M2b macrophages significantly inhibited the mitogen-activated protein kinase (MAPK) signaling pathway.

CONCLUSIONS

These study results demonstrate for the first time that different subtypes of macrophages have different roles in regulating CF activation. M2b macrophages inhibit CF activation, and thus can be considered anti-fibrotic macrophages. M2a macrophages promote CF activation, and thus are pro-fibrotic macrophages.

Plasma Level of Interferon-γ Predicts the Prognosis in Patients With New-Onset Atrial Fibrillation

BACKGROUND

Patients with atrial fibrillation are at increased risk of stroke and mortality. It is not clear if inflammatory biomarkers are associated with stroke and mortality in patients with atrial fibrillation. We aimed to evaluate the predictive value of three inflammatory biomarkers (interleukin [IL]-9, IL-10, and interferon [IFN]-γ) for stroke and mortality in atrial fibrillation.

METHOD

A total of 232 patients with new-onset atrial fibrillation were enrolled and 217 patients were completely followed-up. Peripheral plasma concentrations of cytokines (IL-9, IL-10, and IFN-γ) were measured using Luminex xMAP assays. The association between dichotomous groups of cytokines and outcomes were evaluated by a Cox proportional hazards model. The incremental value of inflammatory biomarkers, in addition to the CHA₂DS₂-VASc score, was also assessed.

RESULTS

Patients were followed-up for a median duration of 27 (interquartile range [IQR], 23-30) months. The elevated plasma level of IFN-γ was an independent risk factor for stroke (hazard ratio [HR], 4.02 [IQR, 1.06-15.34]; p=0.042) and all-cause mortality (HR, 3.93 [IQR, 1.43-10.78]; p=0.008) in patients with atrial fibrillation. Adding high IFN-γ to the CHA₂DS₂-VASc score showed improvement in discrimination and reclassification prediction for stroke and mortality. However, IL-9 and IL-10 had no statistically significant association with stroke and all-cause mortality in patients with atrial fibrillation.

CONCLUSIONS

In this "real-world" cohort of patients with atrial fibrillation, we have shown for the first time that plasma levels of IFN-γ could provide incremental prognostic value supplementary to that obtained from the CHA₂DS₂-VASc scores for predicting of stroke and all-cause mortality.

CTRP9 Ameliorates Atrial Inflammation, Fibrosis, and Vulnerability to Atrial Fibrillation in Post-Myocardial Infarction Rats

Background

Inflammation and fibrosis play an important role in the pathogenesis of atrial fibrillation (AF) after myocardial infarction (MI). CTRP9 (C1q/tumor necrosis factor‐related protein‐9) as a secreted glycoprotein can reverse left ventricle remodeling post‐MI, but its effects on MI‐induced atrial inflammation, fibrosis, and associated AF are unknown.

Methods and Results

MI model rats received adenoviral supplementation of CTRP9 (Ad‐CTRP9) by jugular‐vein injection. Cardiac function, inflammatory, and fibrotic indexes and related signaling pathways, electrophysiological properties, and AF inducibility of atria in vivo and ex vivo were detected in 3 or 7 days after MI. shCTRP9 (short hairpin CTRP9) and shRNA were injected into rat and performed similar detection at day 5 or 10. Adverse atrial inflammation and fibrosis, cardiac dysfunction were induced in both MI and Ad‐GFP (adenovirus‐encoding green fluorescent protein)+MI rats. Systemic CTRP9 treatment improved cardiac dysfunction post‐MI. CTRP9 markedly ameliorated macrophage infiltration and attenuated the inflammatory responses by downregulating interleukin‐1β and interleukin‐6, and upregulating interleukin‐10, in 3 days post‐MI; depressed left atrial fibrosis by decreasing the expressions of collagen types I and III, α‐SMA, and transforming growth factor β1 in 7 days post‐MI possibly through depressing the Toll‐like receptor 4/nuclear factor‐κB and Smad2/3 signaling pathways. Electrophysiologic recordings showed that increased AF inducibility and duration, and prolongation of interatrial conduction time induced by MI were attenuated by CTRP9; moreover, CTRP9 was negatively correlated with interleukin‐1β and AF duration. Downregulation of CTRP9 aggravated atrial inflammation, fibrosis, susceptibility of AF and prolonged interatrial conduction time, without affecting cardiac function.

Conclusions

CTRP9 is effective at attenuating atrial inflammation and fibrosis, possibly via its inhibitory effects on the Toll‐like receptor 4/nuclear factor‐κB and Smad2/3 signaling pathways, and may be an original upstream therapy for AF in early phase of MI.

Vago-Splenic Axis in Signal Transduction of Remote Ischemic Preconditioning in Pigs and Rats

RATIONALE

The signal transduction of remote ischemic conditioning is still largely unknown.

OBJECTIVE

Characterization of neurohumoral signal transfer and vago-splenic axis in remote ischemic preconditioning (RIPC).

METHODS AND RESULTS

Anesthetized pigs were subjected to 60 minutes of coronary occlusion and 180 minutes of reperfusion (placebo+ischemia/reperfusion [PLA+I/R]). RIPC was induced by 4×5/5 minutes of hindlimb I/R 90 minutes before coronary occlusion (RIPC+I/R). Arterial blood samples were taken after placebo or RIPC before I/R. In subgroups of pigs, bilateral cervical vagotomy, splenectomy, or splenic denervation were performed before PLA+I/R or RIPC+I/R, respectively. In pigs with RIPC+I/R, infarct size (percentage of area at risk) was less than in those with PLA+I/R (23±12% versus 45±8%); splenectomy or splenic denervation abrogated (splenectomy+RIPC+I/R: 38±15%; splenic denervation+RIPC+I/R: 43±5%), and vagotomy attenuated (vagotomy+RIPC+I/R: 36±11%) RIPC protection. RIPC increased phosphorylation of STAT3 (signal transducer and activator of transcription 3) in left ventricular biopsies taken at early reperfusion. Splenectomy or splenic denervation, but not vagotomy, abolished this increased phosphorylation. In rats with vagotomy, splenectomy, or splenic denervation, RIPC (3×5/5 minutes of hindlimb occlusion/reperfusion) or placebo was performed, respectively. Hearts were isolated, saline perfused, and subjected to 30/120-minute global I/R. With RIPC, infarct size (percentage of ventricular mass) was less (20±7%) than with placebo (37±6%), and vagotomy, splenectomy, or splenic denervation abrogated RIPC protection (38±12%, 36±9%, and 36±7%), respectively. Rat spleens were isolated, saline perfused, and splenic effluate (SEff) was sampled after infusion with carbachol (SEff_carbachol) or saline (SEff_saline). Pig plasma or SEff was infused into isolated perfused rat hearts subjected to global I/R. Infarct size was less with infusion of RIPC+I/R_plasma+ (24±6%) than with PLA+I/R_plasma (40±8%), vagotomy+PLA+I/R_plasma (39±11%), splenectomy+PLA+I/R_plasma (35±8%), vagotomy+RIPC+I/R_plasma (40±9%), splenectomy+RIPC+I/R_plasma (33±9%), or splenic denervation+RIPC+I/R_plasma (39±8%), respectively. With infusion of SEff_carbachol, infarct size was less than with infusion of SEff_saline (24 [19-27]% versus 35 [32-38]%).

CONCLUSIONS

Activation of a vago-splenic axis is causally involved in RIPC cardioprotection.

Splenectomy may have more complications than currently proven

The spleen has been one of the least understood major organs for centuries. Its significance is relatively well-known today but it seems that all aspects of its activities are not fully understood. Persian medicine (PM) has special views on the function of spleen; many side effects were reported in PM due to spleen dysfunction. On the other hand nowadays splenectomy as a treatment strategy is recommended for some disorders and increasing risk of infections is considered as the most important long term side effect of that. In this study, we hypothesize that splenectomy may have more side effects than currently proven. According to PM, spleen is in close connection with liver, cardiovascular system, stomach, bone, brain and skin, and that is why any kind of spleen dysfunction leads to change in blood viscosity, appetite and bone strength, liver dysfunction, mood and skin disorders, cancer formation and fever. Considering this viewpoint it can be hypothesized such side effects may also occur after splenectomy. Proven complications of splenectomy include hypercoagulated state, cardiovascular events and infectious diseases but there is also some evidence about increased risk of cancer, skin disease like systemic lupus erythematosus, mood disorder such as depression, defective bone formation and impairment of immunity which can be considered as different levels of evidence to confirm the hypothesis. But for some others such as changes in appetite, there are no studies let alone convincing evidence. Future research about theses possible complications may lead to novel results.

Splenic blood-flow response following myocardial infarction in rat

During physiological stress (e.g., exercise, hypoxia), blood flow is shunted to specific anatomical regions to protect critical organs; yet, splenic blood flow in these circumstances remains to be investigated. Despite being classically viewed as a non-critical organ, recent experimental and epidemiological evidence suggests the spleen plays a significant role in cardiovascular pathophysiology. We hypothesized that splenic blood flow is prioritized in the development of heart failure (i.e., chronic state of reduced cardiac output). Five-week-old male Wistar rats were randomized for either myocardial infarction (MI; n = 58) or sham (n = 56) surgery. At 2, 5, and 9 weeks post-surgery, Doppler ultrasound measurements of the splenic, left renal, left common carotid, and left femoral arteries were performed. Cardiac function was assessed at all time points using echocardiography and at 9 weeks post-surgery using invasive hemodynamic analysis. Splenic and cerebral blood flow was preferentially maintained at 9 weeks post-MI, whereas blood flow to the lower limb and kidney were reduced. Spleen size increased by 5 weeks post-MI and remained elevated. Splenic blood flow was maintained in conditions of decreased cardiac output, when other tissues showed decreased blood flow. The maintenance of blood flow in the face of decreased cardiac output indicates that splenic function is being prioritized during heart failure.

MicroRNA-30c suppresses the pro-fibrogenic effects of cardiac fibroblasts induced by TGF-β1 and prevents atrial fibrosis by targeting TGFβRII

Atrial fibrosis serves as an important contributor to atrial fibrillation (AF). Recent data have suggested that microRNA-30c (miR-30c) is involved in fibrotic remodelling and cancer development, but the specific role of miR-30c in atrial fibrosis remains unclear. The purpose of this study was to investigate the role of miR-30c in atrial fibrosis and its underlying mechanisms through in vivo and in vitro experiments. Our results indicate that miR-30c is significantly down-regulated in the rat abdominal aortic constriction (AAC) model and in the cellular model of fibrosis induced by transforming growth factor-β1 (TGF-β1). Overexpression of miR-30c in cardiac fibroblasts (CFs) markedly inhibits CF proliferation, differentiation, migration and collagen production, whereas decrease in miR-30c leads to the opposite results. Moreover, we identified TGFβRII as a target of miR-30c. Finally, transferring adeno-associated virus 9 (AAV9)-miR-30c into the inferior vena cava of rats attenuated fibrosis in the left atrium following AAC. These data indicate that miR-30c attenuates atrial fibrosis via inhibition of CF proliferation, differentiation, migration and collagen production by targeting TGFβRII, suggesting that miR-30c might be a novel potential therapeutic target for preventing atrial fibrosis.

Extensively re-organized systemic lymph nodes provide a feasible environment for self-reactivity in lupus-prone NZB × NZW F1 mice

Lymphadenopathy is a frequently observed symptom in systemic lupus erythematosus, although the immunological role of lymph nodes (LNs) in systemic autoimmunity remains largely unknown. Here, we performed comprehensive and systematic analyses of LNs in lupus-prone NZB × NZW F1 (BWF1) mice, demonstrating extensive tissue re-organization of the systemic LNs with follicular expansion, hyper germinal center (GC) formation, atrophy of the paracortical T-cell area and expansion of the medulla in aged BWF1 mice bearing glomerulonephritis. The proportion of B cells was significantly increased in these reactive LNs but not in the spleen, and lymphocyte subsets involved in antibody production, i.e. GC B cells, follicular helper T cells and plasma cells, were elevated. Draining LNs of the affected organs, such as the renal and cervical nodes, showed enhanced tissue re-organization and accumulation of effector lymphocytes, suggesting the presence of a positive feedback loop of regional responses. LN cells isolated from disease-bearing animals produced anti-DNA antibody, indicating activation of autoreactive lymphocytes in situ. The substantial development of disease and LN alterations in mice that received a splenectomy at a young age points to the importance of other secondary lymphoid organs, most likely LNs, for the progression of autoimmune responses independent of the spleen. Taken together, our findings highlight the value of taking LN alterations and activities into consideration for understanding the pathogenesis of systemic autoimmunity.

Mast Cells Play an Important Role in the Pathogenesis of Hyperglycemia-Induced Atrial Fibrillation

BACKGROUND AND OBJECTIVES

Recently, it was reported that mast cells (MCs) could underlie the mechanisms of several cardiovascular diseases. However, the role of MCs in diabetes-induced atrial fibrillation (AF) has not been notably investigated. We tested the hypothesis that MC deficiency attenuates hyperglycemia-induced AF in mice.

METHODS AND RESULTS

Mast cell-deficient W/W(v)  mice, and congenic +/+ littermates (WT) were divided into either the vehicle (VEH)-injection group or the streptozotocin (STZ)-injection group (MCKO-VEH, MCKO-STZ, WT-VEH, and WT-STZ groups). On day 28 of our studies, we observed that (1) STZ-induced hyperglycemia increased MC infiltration in the left atrium (LA) in WT mice (P < 0.01), (2) atrium isolated from the WT-STZ group showed inhomogeneous interstitial fibrosis, abundant infiltration of macrophages, and enhanced apoptosis compared to the WT-VEH group (P < 0.01, P < 0.01, P < 0.05, respectively). However, the changes observed in the WT-STZ group were significantly attenuated in the MCKO-STZ mice. In addition, we observed that (3) messenger RNA levels of tumor necrosis factor-α, monocyte chemoattractant protein-1, interleukin-1β, transforming growth factor-β, and collagen-1 in the LA were increased in the WT-STZ group, but not in the MCKO-STZ group, (4) STZ-induced hyperglycemia increased AF induction and prolonged interatrial conduction time in the WT mice, which were not observed in the MCKO mice, and that (5) hyperglycemia-enhanced atrial production of reactive oxygen species (ROS) was equally observed in the WT and MCKO mice.

CONCLUSIONS

Our results suggest that MCs contribute to the pathogenesis of hyperglycemia-induced AF via enhancement of inflammation and fibrosis.