sST2 Predicts Short Term Therapy Success in Patients with Therapy Resistant Hypertension after Renal Sympathetic Denervation

Background: Renal sympathetic denervation (RSD) has provided promising data in its ability to treat therapy resistant arterial hypertension. The effect of RSD on sST-2, a promising biomarker for risk stratification in cardiovascular diseases, has so far not been systematically studied. Methods: We evaluated serum levels of sST-2 and clinical parameter including left ventricular mass (LVM) in 54 patients with resistant hypertension (RH) undergoing bilateral RSD at baseline as well as at one and/or three months. Results: After RSD, mean office blood pressure showed a significant decrease after one month (p < 0.001). On echocardiography a reduction of LVM was observed at three months (p < 0.01). This was accompanied by a significant decrease of sST-2 levels at three months (sST-2 baseline: 6310.1 ± 3246.0 pg/mL vs. sST-2 three months: 4703.8 ± 1585.9 pg/mL, p = 0.048). Furthermore, baseline sST-2 levels were positively correlated with systolic blood pressure at one month (r = 0.514, p < 0.01) but not three months, indicating a potential predictive value of sST-2 for early intervention success. Conclusion: In patients with RH, RSD is associated with a significant decrease of sST-2 levels after three months, indicating sST-2 to be involved in remodeling processes after RSD. Furthermore, lower sST-2 levels at baseline might be a potential predictor of early intervention success of RSD.

Enhanced Expression and Function of Renal SGLT2 (Sodium-Glucose Cotransporter 2) in Heart Failure: Role of Renal Nerves

Background: Recent clinical studies demonstrate that SGLT2 (sodium-glucose cotransporter 2) inhibitors ameliorate heart failure (HF). The present study was conducted to assess the expression and function of renal SGLT2 and the influence of enhanced renal sympathetic tone in HF. Methods: Four weeks after coronary artery ligation surgery to induce HF, surgical bilateral renal denervation (RDN) was performed in rats. Four groups of rats (Sham-operated control [Sham], Sham+RDN, HF and HF+RDN; n=6/group) were used. Immunohistochemistry and Western blot analysis were performed to evaluate the renal SGLT2 expression. One week after RDN (5 weeks after induction of HF), intravenous injection of SGLT2 inhibitor dapagliflozin were performed to assess renal excretory responses. In vitro, human embryonic kidney cells were used to investigate the fractionation of SGLT2 after norepinephrine treatment. Results: In rats with HF, (1) SGLT2 expression in the proximal tubule of the kidney was increased; (2) the response of increases in urine flow, sodium excretion, and glucose excretion to dapagliflozin were greater; and (3) RDN attenuated renal SGLT2 expression and normalized renal functional responses to dapagliflozin. In vitro, norepinephrine promoted translocation of SGLT2 to the cell membrane. Conclusions: These results indicate that the enhanced tonic renal sympathetic nerve activation in HF increases the expression and functional activity of renal SGLT2. Potentiated trafficking of SGLT2 to cell surface in renal proximal tubules mediated by norepinephrine may contribute to this functional activation of SGLT2 in HF. These findings provide critical insight into the underlying mechanisms for the beneficial effects of SGLT2 inhibitors on HF reported in the clinical studies.

IL (Interleukin)-17A Acts in the Brain to Drive Neuroinflammation, Sympathetic Activation, and Hypertension

IL (Interleukin)-17A is a key inflammatory mediator contributing to chronic tissue inflammation. The present study sought to determine whether IL-17A plays a role in regulating neuroinflammation, hemodynamics, and sympathetic outflow in normal and hypertensive animals. In urethane-anesthetized rats, intravenous injection of IL-17A induced dramatic and prolonged increases in blood pressure, heart rate, and renal sympathetic nerve activity, which were significantly attenuated by an IL-17RA (IL-17 receptor A) siRNA in the hypothalamic paraventricular nucleus (PVN). Either intracerebroventricular or PVN microinjection of IL-17A also elicited a similar excitatory response in blood pressure, heart rate, and renal sympathetic nerve activity. Intravenous injection of IL-17A upregulated the mRNA level of IL-17A, IL-17F, and IL-17RA in the PVN. Additionally, intravenous injection of IL-17A activated brain-resident glial cells and elevated the gene expression of inflammatory cytokines and chemokines in the PVN, which were markedly diminished by PVN microinjection of IL-17RA siRNA. Pretreatments with microglia or astrocyte inhibitors attenuated the increase in blood pressure, heart rate, and renal sympathetic nerve activity in response to PVN IL-17A. Moreover, intracerebroventricular injection of IL-17A activated TGF (transforming growth factor)-β activated kinase 1, p44/42 mitogen-activated protein kinase, and transcriptional nuclear factor κB in the PVN. IL-17A interacted with tumor necrosis factor-α or IL-1β synergistically to exaggerate its influence on hemodynamic and sympathetic responses. Central intervention suppressing IL-17RA in the PVN significantly reduced angiotensin II–induced hypertension, neuroinflammation, and sympathetic tone in the rats. Collectively, these data indicated that IL-17A in the brain promotes neuroinflammation to advance sympathetic activation and hypertension, probably by a synergistic mechanism involving the interaction with various inflammatory mediators within the brain.

Role of Renal Sympathetic Nerves in GLP‐1 (Glucagon‐Like Peptide‐1) Receptor Agonist Exendin‐4‐Mediated Diuresis and Natriuresis in Diet‐Induced Obese Rats

Background The gut‐derived hormone GLP‐1 (glucagon‐like peptide‐1) exerts beneficial effects against established risk factors for chronic kidney disease. GLP‐1 influences renal function by stimulating diuresis and natriuresis and thus lowering arterial blood pressure. The role of the sympathetic nervous system has been implicated as an important link between obesity with elevated arterial pressure and chronic kidney disease. The primary aim of this study was to determine the contribution of renal sympathetic nerves on intrapelvic GLP‐1‐mediated diuresis and natriuresis in high‐fat diet (HFD)‐induced obese rats. Methods and Results Obesity was induced in rats by HFD for 12 weeks, followed by either surgical bilateral renal denervation or chronic subcutaneous endopeptidase neprilysin inhibition by sacubitril for a week. Diuretic and natriuretic responses to intrapelvic administration of the GLP‐1R (GLP‐1 receptor) agonist exendin‐4 were monitored in anesthetized control and HFD rats. Renal GLP‐1R expression and neprilysin expression and activity were measured. The effects of norepinephrine on the expression of GLP‐1R and neprilysin in kidney epithelial LLC‐PK1 cells were also examined. We found that diuretic and natriuretic responses to exendin‐4 were significantly reduced in the HFD obese rats compared with the control rats (cumulative urine flow at 40 minutes, 387±32 versus 650±65 µL/gkw; cumulative sodium excretion at 40 minutes, 42±5 versus 75±10 µEq/gkw, P <0.05). These responses in the HFD rats were restored after ablation of renal nerves (cumulative urine flow at 40 minutes, 625±62 versus 387±32 µL/gkw; cumulative sodium excretion at 40 minutes, 70±9 versus 42±5 µEq/gkw, P <0.05). Renal denervation induced significant reductions in arterial pressure and heart rate responses to intrapelvic GLP‐1 in the HFD rats. Renal denervation also significantly increased the GLP‐1R expression and reduced neprilysin expression and activity in renal tissues from the HFD rats. Chronic subcutaneous neprilysin inhibition by sacubitril increased GLP‐1–induced diuretic and natriuretic effects in the HFD rats. Finally, exposure of the renal epithelial cells to norepinephrine in vitro led to downregulation of GLP‐1R expression but upregulation of neprilysin expression and activity. Conclusions These results suggest that renal sympathetic nerve activation contributes to the blunted diuretic and natriuretic effects of GLP‐1 in HFD obese rats. This study provides significant novel insight into the potential renal nerve–neprilysin–GLP‐1 pathway involved in renal dysfunction during obesity that leads to hypertension.

Comparison of Long‐Term Outcomes for Responders Versus Non‐Responders Following Renal Denervation in Resistant Hypertension

Background Recent trial results support the efficacy of renal sympathetic denervation in lowering blood pressure (BP). While BP reduction in general is associated with a clinically meaningful reduction in cardiovascular events and mortality, such a relationship has not been described for patients undergoing renal sympathetic denervation. Methods and Results Clinical events were assessed in patients who underwent renal sympathetic denervation at our center using telephone‐ and clinical follow‐up, interviews with general practitioners, as well as review of hospital databases. Event rates were compared between BP responders (≥5 mm Hg 24‐hour ambulatory BP reduction) and non‐responders; 296 patients were included. Compared with baseline, 24‐hour systolic ambulatory BP was reduced by 8.3±12.2 mm Hg and diastolic BP by 4.8±7.0 mm Hg ( P <0.001 for both) after 3 months. One hundred eighty patients were classified as BP responders and 116 as non‐responders. During a median follow‐up time of 48 months, significantly less major adverse cardiovascular events (cardiovascular death, stroke, myocardial infarction, critical limb ischemia, renal failure) occurred in responders than in non‐responders (22 versus 23 events, hazard ratio [HR], 0.53 [95% CI, 0.28 to 0.97], P =0.041). This was consistent after adjustment for potential confounders as well as confirmed by propensity‐score matching. A proportional relationship was found between BP reduction after 3 months and frequency of major adverse cardiovascular events (HR, 0.75 [95% CI, 0.58 to 0.97] per 10 mm Hg 24‐hour systolic ambulatory BP reduction). Conclusions Based on these observational data, blood pressure response to renal sympathetic denervation is associated with improved long‐term clinical outcome.

Optimal Strategy for HIFU-Based Renal Sympathetic Denervation in Canines

Background: The association between the treatment efficacy and safety of high-intensity focused ultrasound (HIFU)-based renal sympathetic denervation (RDN) and the acoustic energy dose applied has not been fully studied and may provide important understanding of the mechanism that led to failure of the WAVE IV trial. The objective of this study was to externally deliver different HIFU doses to canines for RDN treatment and to investigate the optimal energy dose for HIFU-based RDN.Methods: Thirty canines were divided into five RDN groups according to dose of acoustic energy applied, and a sham control group that consisted of four canines was used for comparisons. All animals in the RDN groups underwent the RDN procedure with different acoustic energy doses, while in the sham control group, renal arteries were harvested without being subjected to acoustic energy delivery and were imaged using color Doppler flow imaging (CDFI). Blood pressure (BP) was recorded, and blood samples were collected before the RDN procedure and at 28 days after the RDN procedure. Histological examinations and measurement of renal tissue norepinephrine concentration were performed in all retrieved samples.Results: Suppression of BP was significant in the 300 W (15.17/8.33 ± 1.47/1.21 mmHg), 250 W (14.67/9.33 ± 1.21/1.37 mmHg), and 200 W (13.17/9.17 ± 2.32/1.84 mmHg) groups. Semiquantitative histological assessment of periarterial nerves around the kidney revealed that target nerves in the 300 W (9.77 ± 0.63), 250 W (9.42 ± 0.67), and 200 W (9.58 ± 0.54) groups had the highest nerve injury scores, followed by the 150 W group (5.29 ± 0.62). Furthermore, decreased renal tissue norepinephrine concentration, together with decreased expression of tyrosine hydroxylase in the 300, 250, and 200 W groups demonstrated effective sympathetic depression following sufficient acoustic energy deposition. However, the renal artery injury score in the 300 W group (0.93 ± 0.13) was significantly higher than in the other groups (p &lt; 0.001).Conclusion: This study provides evidence that RDN effectiveness is based on the energy dose delivered and that 200–250 W is effective and safe in normal-sized canines.