Chamber-specific regulation of atrial natriuretic peptide secretion in cardiac hypertrophy: atrial wall dynamics in the ANP secretion

Mitofilin in cardiovascular diseases: Insights into the pathogenesis and potential pharmacological interventions

The impact of mitochondrial dysfunction on the pathogenesis of cardiovascular disease is increasing. However, the precise underlying mechanism remains unclear. Mitochondria produce cellular energy through oxidative phosphorylation while regulating calcium homeostasis, cellular respiration, and the production of biosynthetic chemicals. Nevertheless, problems related to cardiac energy metabolism, defective mitochondrial proteins, mitophagy, and structural changes in mitochondrial membranes can cause cardiovascular diseases via mitochondrial dysfunction. Mitofilin is a critical inner mitochondrial membrane protein that maintains cristae structure and facilitates protein transport while linking the inner mitochondrial membrane, outer mitochondrial membrane, and mitochondrial DNA transcription. Researchers believe that mitofilin may be a therapeutic target for treating cardiovascular diseases, particularly cardiac mitochondrial dysfunctions. In this review, we highlight current findings regarding the role of mitofilin in the pathogenesis of cardiovascular diseases and potential therapeutic compounds targeting mitofilin.

The sustainable antihypertensive and target organ damage protective effect of transcranial focused ultrasound stimulation in spontaneously hypertensive rats

OBJECTIVE

In this study, we aimed to investigate the sustainable antihypertensive effects and protection against target organ damage caused by low-intensity focused ultrasound (LIFU) stimulation and the underlying mechanism in spontaneously hypertensive rats (SHRs) model.

METHODS AND RESULTS

SHRs were treated with ultrasound stimulation of the ventrolateral periaqueductal gray (VlPAG) for 20 min every day for 2 months. Systolic blood pressure (SBP) was compared among normotensive Wistar-Kyoto rats, SHR control group, SHR Sham group, and SHR LIFU stimulation group. Cardiac ultrasound imaging and hematoxylin-eosin and Masson staining of the heart and kidney were performed to assess target organ damage. The c-fos immunofluorescence analysis and plasma levels of angiotensin II, aldosterone, hydrocortisone, and endothelin-1 were measured to investigate the neurohumoral and organ systems involved. We found that SBP was reduced from 172 ± 4.2 mmHg to 141 ± 2.1 mmHg after 1 month of LIFU stimulation, P  < 0.01. The next month of treatment can maintain the rat's blood pressure at 146 ± 4.2 mmHg at the end of the experiment. LIFU stimulation reverses left ventricular hypertrophy and improves heart and kidney function. Furthermore, LIFU stimulation enhanced the neural activity from the VLPAG to the caudal ventrolateral medulla and reduced the plasma levels of ANGII and Aldo.

CONCLUSION

We concluded that LIFU stimulation has a sustainable antihypertensive effect and protects against target organ damage by activating antihypertensive neural pathways from VLPAG to the caudal ventrolateral medulla and further inhibiting the renin-angiotensin system (RAS) activity, thereby supporting a novel and noninvasive alternative therapy to treat hypertension.

Amelioration of Hypertension by Oryeongsan through Improvements of Body Fluid and Sodium Balance: Roles of the Renin-Angiotensin System and Atrial Natriuretic Peptide System

Oryeongsan (Wulingsan in China and Goreisan in Japan), a formula composed of five herbal medicines, has long been used for the treatment of imbalance of the body fluid homeostasis in Asian countries. However, the mechanism by which Oryeongsan (ORS) improves the impaired body fluid and salt metabolism is not clearly defined. The present study was performed to define the role of the cardiorenal humoral system in the ORS-induced changes in blood pressure and renal function in hypertension. Experiments were performed in normotensive and two-kidney, one-clip hypertensive rats. Changes in the fluid and salt balance were measured in rats individually housed in metabolic cages. Changes in the systemic and local renin-angiotensin system (RAS) and cardiac natriuretic peptide hormone system (NPS) were evaluated. ORS water extract was administered by oral gavage (100 mg/kg daily) for 3 weeks. ORS induced diuresis and natriuresis along with an increase in glomerular filtration rate and downregulation of the Na⁺/H⁺ exchanger 3 (NHE3) and aquaporin 2 expression in the renal cortex and medulla, respectively. Furthermore, treatment with ORS significantly decreased systolic blood pressure with contraction of body sodium and water accumulation in hypertensive rats. ORS-induced changes were accompanied by modulation of the RAS and NPS, downregulation of the systemic RAS and cardiorenal expression of angiotensin-converting enzyme (ACE) and angiotensin II subtype 1 (AT₁) receptor, and upregulation of the plasma ANP concentration and cardiorenal expression of ANP, ACE2, Mas receptor, and AT₂ receptor. These findings indicate that ORS induces beneficial effects on the high blood pressure through modulation of the RAS and NPS of the cardiorenal system, suppression of the prohypertensive ACE-AT₁ receptor pathway and NHE3, accentuation of the antihypertensive ACE2-Mas axis/AT₂ receptor pathway in the kidney, suppression of the systemic RAS, and elevation of the plasma ANP levels and its synthesis in the heart. The present study provides a biological basis for the use of ORS in the treatment of impaired volume and pressure homeostasis.

Oryeongsan (Wulingsan) ameliorates impaired ANP secretion of atria from spontaneously hypertensive rats

Oryeongsan (ORS), a herbal medicine formula, has long been used for the treatment of impaired body water balance in Asian countries. Recently, it was shown that ORS administration modulates the renin-angiotensin system (RAS). Purpose of the present study was to determine characteristics of atrial ANP secretion and effects of ORS on the secretion in the atria from spontaneously hypertensive rats (SHR). Normotensive WKY groups (WKY-V, WKY-ORS, WKY-LOS) and hypertensive SHR groups (SHR-V, SHR-ORS, SHR-LOS) treated with vehicle, ORS, and losartan as a positive control group, respectively, were used. Experiments were performed in perfused beating atria (1.3 Hz) allowing atrial distension, acetylcholine (ACh) stimulation, and serial collection of atrial perfusates. The secreted ANP concentration was measured using radioimmunoassay. Interstitial fluid (ISF) translocation was measured using [³H]inulin clearance. Stepwise increase in atrial distension by 1.1, 2.0, and 2.7 cmH₂O above basal distension further increased ANP secretion proportionally in the atria from WKY-V, but the response was significantly suppressed in the atria from SHR-V. Cardiomyocyte ANP release, the first step of atrial ANP secretion, was suppressed in the atria from SHR-V compared to those from WKY-V (-8.02 ± 2.86, -15.86 ± 2.27, and -20.09 ± 3.62%; n = 8, for SHR-V vs. 8.59 ± 2.81, 15.65 ± 7.14, and 38.12 ± 8.28%; n = 8, for WKY-V; p < 0.001 for all stepwise distension, respectively). Chronic treatment with ORS reversed the suppressed ANP release in atria from SHR-ORS group (6.76 ± 3.92, 9.12 ± 2.85, and 28.79 ± 1.79% for SHR-ORS; n = 5 vs. SHR-V; n = 8; p = 0.01, p < 0.001, p < 0.001, respectively). The effects of ORS were comparable to those of losartan. Trans-endocardial translocation of ISF, the second step of atrial ANP secretion was similar in the atria from the hypertensive SHR-V and normotensive WKY-V. ACh-induced ANP secretion and cardiomyocyte ANP release were also suppressed in the atria from SHR-V compared to WKY-V and ORS reversed the suppression. These findings were accompanied with accentuation of the AT₁ receptor expression and suppression of the AT₂/Mas receptor, M₂ mACh receptor and GIRK4, a molecular component of K_ACh channel, expression in the atria from SHR-V. Further, treatment with ORS or losartan reversed the expressions in the groups of SHR-ORS and SHR-LOS. These results show that ANP secretion is suppressed in the atria from SHR in association with accentuation of AT₁ receptor and suppression of AT₂/Mas receptor and K_ACh channel expression. Treatment with ORS ameliorates impaired ANP secretion through improving cardiomyocyte ANP release with modulation of the cardiac RAS and muscarinic signaling. These findings provide experimental evidence which supports the effect of ORS on the regulation of atrial ANP secretion in the atria from SHR.

Deciphering the effective combinatorial components from Si-Miao-Yong-An decoction regarding the intervention on myocardial hypertrophy

ETHNOPHARMACOLOGICAL RELEVANCE

Si-Miao-Yong-An decoction (SMYAD), a classical traditional Chinese medicine (TCM) formula, has been used to treat various cardiovascular diseases in clinics.

AIM OF THE STUDY

The aim of this study is to investigate the effective combinatorial components from SMYAD and its mechanism regarding the intervention on myocardial hypertrophy.

MATERIALS AND METHODS

SMYAD constituents absorbed in rat plasma and heart were identified using UHPLC Q-Exactive-Orbitrap MS/MS. The identified constituents in SMYAD were further analyzed using ADMET (absorption, distribution, metabolism, excretion and toxicity) prediction and molecular docking. The effective constituents were identified using isoproterenol (ISO)-induced H9c2 cardiomyocyte hypertrophy, and neochlorogenic acid (NCA), chlorogenic acid (CA), cryptochlorogenic acid (CCA), isochlorogenic acid C (ICAC), angoroside C (AGDC), isochlorogenic acid A (ICAA), sweroside (SRD), and harpagide (HPD) in SMYAD extract were quantified by HPLC for compatibility. Finally, anti-hypertrophic activities of candidate effective combinatorial components, which were prepared according to the determined molar concentration ratio of effective constituents using reference substance solution, were analyzed using immunofluorescence staining and Quantitative real-time PCR. The expression levels of PI3Kα, p-ERK, p-Akt, Akt, p-mTOR, mTOR and HIF-1α were measured using Western blot.

RESULTS

32 prototypes of SMYAD were identified from plasma and heart tissue of rat. Combining with ADMET prediction, 31 dominant constituents were focused. Based on HIF-1 pathway identified in preliminary result, 17 targets were focused, which were used to dock with 31 constituents. 27 constituents were therefore hit as the potential effective constituents of SMYAD in inhibiting myocardial hypertrophy. Bioactivity evaluation showed that NCA, CA, CCA, ICAC, AGDC, ICAA, SRD, and HPD significantly inhibited the increase of H9c2 cell surface area induced by ISO. Except for ICAA and AGDC, the remaining 6 effective constituents, showing a certain inhibitory effect on ISO-induced ANP mRNA overexpression at high and low concentrations, participated in compatibility based on the molar concentration ratio determined by HPLC. Effective combinatorial components composed of the 6 effective constituents (effective combinatorial components ABC) showed significant inhibitory effect on the increase of cell surface area, and the overexpression of ANP and β-MHC mRNA in H9c2 cells induced by ISO. Moreover, effective combinatorial components ABC significantly inhibited the protein overexpressions of p-Akt, p-mTOR and HIF-1α. Based on the results, we put forward the strategy of "Focusing constituents" and "Focusing targets" for the effective constituents research of TCM formula.

CONCLUSION

Effective combinatorial components ABC composed of NCA, CA, CCA, ICAC, SRD and HPD from SMYAD inhibited ISO-induced cardiomyocyte hypertrophy and down-regulated expression of ANP and β-MHC mRNA through the inactivation of Akt/mTOR/HIF-1α pathway.

Mid-regional pro-atrial natriuretic peptide independently predicts short-term mortality in COVID-19

BACKGROUND

Mid-regional pro-atrial natriuretic peptide (MR-proANP) is a strong prognostic marker in several inflammatory, respiratory and cardiovascular conditions, but has not been studied in COVID-19 yet.

METHODS

This prospective, observational study of patients with COVID-19 infection was conducted from 6 June to 26 November 2020 in different wards of a tertiary hospital. MR-proANP, N-terminal pro-brain natriuretic peptide (NT-proBNP) and high-sensitive cardiac troponin I levels on admission were collected and tested for their association with disease severity and 28-day mortality.

RESULTS

A total of 213 eligible patients with COVID-19 were included in the final analyses of whom 13.2% (n = 28) died within 28 days. Median levels of MR-proANP at admission were significantly higher in nonsurvivors (307 pmol/L IQR, [161 - 532] vs 75 pmol/L [IQR, 43 - 153], P < .001) compared to survivors and increased with disease severity and level of hypoxaemia. The area under the ROC curve for MR-proANP predicting 28-day mortality was 0.832 (95% CI 0.753 - 0.912, P < .001). An optimal cut-off point of 160 pmol/L yielded a sensitivity of 82.1% and a specificity of 76.2%. MR-proANP was a significant predictor of 28-day mortality independent of clinical confounders, comorbidities and established prognostic markers of COVID-19 (HR 2.77, 95% CI 1.21 - 6.37; P = .016), while NT-proBNP failed to independently predict 28-day mortality and had a numerically lower AUC compared to MR-proANP.

CONCLUSION

Higher levels of MR-proANP at admission are associated with disease severity of COVID-19 and act as a powerful and independent prognostic marker of 28-day mortality.