New Insights Into the Role of Inflammation in the Brain in Heart Failure

Interleukin 17A Contributes to Blood-Brain Barrier Disruption of Hypothalamic Paraventricular Nucleus in Rats With Myocardial Infarction

BACKGROUND

Elevated inflammatory cytokines in the periphery have been identified as active contributors to neuroinflammation and sympathetic overactivity in heart failure (HF). Yet, the exact mechanisms by which these cytokines breach the blood-brain barrier (BBB) to exert their effects on the brain remain elusive. Interleukin 17A has been linked to BBB disruption in various neurologic disorders, and its levels were significantly augmented in circulation and the brain in HF. The present study aimed to determine whether the BBB integrity was compromised within the hypothalamic paraventricular nucleus (PVN), and if so, whether interleukin 17A contributes to BBB disruption in myocardial infarction-induced HF.

METHODS AND RESULTS

Male Sprague-Dawley rats underwent coronary artery ligation to induce HF or sham surgery. Some HF rats received bilateral PVN microinjections of an interleukin 17 receptor A small interfering RNA or a scrambled small interfering RNA adeno-associated virus. Four weeks after coronary artery ligation, the permeability of the BBB was evaluated by intracarotid injection of fluorescent dyes (fluorescein isothiocyanate-dextran 10 kDa+rhodamine-dextran 70 kDa). Compared with sham-operated rats, HF rats exhibited an elevated extravasation of fluorescein isothiocyanate-dextran 10 kDa within the PVN but not in the brain cortex. The plasma interleukin 17A levels were positively correlated with fluorescein isothiocyanate 10 kDa extravasation in the PVN. The expression of caveolin-1, a transcytosis marker, was augmented, whereas the expression of tight junction proteins was diminished in HF rats. Interleukin 17 receptor A was identified within the endothelium of PVN microvessels. Treatment with interleukin 17 receptor A small interfering RNA led to a significant attenuation of fluorescein isothiocyanate 10 kDa extravasation in the PVN and reversed expression of caveolin-1 and tight junction-associated proteins in the PVN.

CONCLUSIONS

Collectively, these data indicate that BBB permeability within the PVN is enhanced in HF and is likely attributable to increased interleukin 17A/interleukin 17 receptor A signaling in the BBB endothelium, by promoting caveolar transcytosis and degradation of tight junction complexes.

The Brain-Heart Axis: Neuroinflammatory Interactions in Cardiovascular Disease

PURPOSE OF REVIEW

The role of neuroimmune modulation and inflammation in cardiovascular disease has been historically underappreciated. Physiological connections between the heart and brain, termed the heart-brain axis (HBA), are bidirectional, occur through a complex network of autonomic nerves/hormones and cytokines, and play important roles in common disorders.

RECENT FINDINGS

At the molecular level, advances in the past two decades reveal complex crosstalk mediated by the sympathetic and parasympathetic nervous systems, the renin-angiotensin aldosterone and hypothalamus-pituitary axes, microRNA, and cytokines. Afferent pathways amplify proinflammatory signals via the hypothalamus and brainstem to the periphery, promoting neurogenic inflammation. At the organ level, while stress-mediated cardiomyopathy is the prototypical disorder of the HBA, cardiac dysfunction can result from a myriad of neurologic insults including stroke and spinal injury. Atrial fibrillation is not necessarily a causative factor for cardioembolic stroke, but a manifestation of an abnormal atrial substrate, which can lead to the development of stroke independent of AF. Central and peripheral neurogenic proinflammatory factors have major roles in the HBA, manifesting as complex bi-directional relationships in common conditions such as stroke, arrhythmia, and cardiomyopathy.

Yixin Granules Reduce Myocardial Inflammation and Fibrosis in Rats with Heart Failure by Inhibiting the Expression of ADAMTS8

Yixin granules are medications modified from a Chinese prescription (Sheng Xian Tang) that has been used to alleviate shortness of breath. ADAM metallopeptidase with thrombospondin type 1 motif 8 (ADAMTS8) is upregulated in the myocardium of patients with dilated cardiomyopathy. Its high expression is associated with tumor necrosis factor (TNF) -α and myocardial fibrosis. This study aimed to explore the effect of Yixin granules on heart failure (HF) in rats and whether this effect is correlated with ADAMTS8 to provide new ideas for the treatment of HF.HF rat models were established by ligation of the left anterior descending coronary artery. Model rats were injected with adeno-associated virus vectors for the overexpression of ADAMTS8 and/or treated with Yixin granules for 4 weeks. Hematoxylin-eosin and Masson staining were used to detect myocardial injury and fibrosis, respectively. Reverse transcription polymerase chain reaction, western blotting, and/or enzyme-linked immunosorbent assay were used to detect the expression of ADAMTS8, TNF-α, interleukin (IL) -1β, IL-6, collagen I, collagen III, and α-smooth muscle actin in myocardium. The myocardial infarction area of rats was measured using 2,3,5-triphenyltetrazolium chloride staining.ADAMTS8 was upregulated in the myocardium of HF rats. Yixin granule treatment improved left ventricular contractility and reduced ADAMTS8 expression, myocardial injury, inflammation, and fibrosis in HF rats. ADAMTS8 overexpression aggravated myocardial injury, inflammation, and fibrosis. Moreover, ADAMTS8 overexpression counteracted the cardioprotective effects of Yixin granules.Yixin granules may reduce myocardial inflammation and fibrosis in HF rats by inhibiting the expression of ADAMTS8.

Quantitative effects of sodium–glucose cotransporter-2 inhibitors dapagliflozin and empagliflozin on quality of life in heart failure patients

The aim of the present study is to investigate the quantitative effects of sodium–glucose cotransporter-2 (SGLT-2) inhibitors on the quality of life in heart failure (HF) patients. A total of 14,674 HF patients from two dapagliflozin and three empagliflozin studies is included for analysis via the nonlinear mixed-effect modeling (NONMEM) software, among which the change rate of the Kansas City Cardiomyopathy Questionnaire (KCCQ) score is used as the evaluation index. There is no significant difference in the pharmacodynamics influencing the quality of life in HF patients between the SGLT-2 inhibitors: 10 mg/day dapagliflozin and 10 mg/day empagliflozin. For the clinical summary score (CSS), total symptom score (TSS), and overall summary score (OSS), the Emax of the SGLT-2 inhibitors on the quality of life in HF patients is 3.74%, 4.43%, and 4.84%, respectively, and ET50 is 2.23, 4.37, and 7.15 weeks, respectively. In addition, the time duration of achieving 25%, 50%, 75%, and 80% Emax is 0.75, 2.23, 6.69, and 8.92 weeks for the CSS; 1.46, 4.37, 13.11, and 17.48 weeks for the TSS; and 2.39, 7.15, 21.45, and 28.6 weeks for the OSS, respectively. Therefore, to reach the plateau period (80% of Emax) of SGLT-2 inhibitors on the CSS, TSS, and OSS, 10 mg/day dapagliflozin (or 10 mg/day empagliflozin) is required to be taken for 8.92 weeks, 17.48 weeks, and 28.6 weeks, respectively. This is the first time that the quantitative effects of SGLT-2 inhibitors on the quality of life in HF patients are being explored.

Reducing brain TACE activity improves neuroinflammation and cardiac function in heart failure rats

Tumor necrosis factor (TNF)-α converting enzyme (TACE) is a key metalloprotease mediating ectodomain shedding of a variety of inflammatory mediators, substrates, and growth factors. We previously reported that TACE-mediated production of TNF-α in the hypothalamic paraventricular nucleus (PVN) contributes to sympathetic excitation in heart failure (HF). Here, we sought to determine whether central interventions in TACE activity attenuate neuroinflammation and improve cardiac function in heart failure. Myocardial infarction-induced HF or sham-operated (SHAM) rats were treated with bilateral paraventricular nucleus microinjection of a TACE siRNA or a 4-week intracerebroventricular (ICV) infusion of the TACE inhibitor TAPI-0. Compared with SHAM rats, scrambled siRNA-treated HF rats had higher TACE levels in the PVN along with increased mRNA levels of TNF-α, TNF-α receptor 1 and cyclooxygenase-2. The protein levels of TNF-α in cerebrospinal fluid and phosphorylated (p-) NF-κB p65 and extracellular signal-regulated protein kinase (ERK)1/2 in the PVN were also elevated in HF rats treated with scrambled siRNA. The expression of these inflammatory mediators and signaling molecules in the PVN of HF rats were significantly attenuated by TACE siRNA. Interestingly, the mRNA level of TNF-α receptor 2 in the PVN was increased in HF treated with TACE siRNA. Moreover, sympathetic excitation, left ventricular end-diastolic pressure, pulmonary congestion, and cardiac hypertrophy and fibrosis were reduced by PVN microinjection of TACE siRNA. A 4-week treatment with intracerebroventricular TAPI-0 had similar effects to ameliorate these variables in HF rats. These data indicate that interventions suppressing TACE activity in the brain mitigate neuroinflammation, sympathetic activation and cardiac dysfunction in HF rats.