Some Aspects of the Renin-Angiotensin-System in Hemodialysis Patients

Renin-angiotensin system inhibition and mortality in patients undergoing dialysis with coronary artery disease: insights from a multi-center observational study

BACKGROUND

While the survival benefits of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) are firmly established in the general population, their efficacy within patient undergoing dialysis with coronary artery disease (CAD) remains controversial.

METHODS

Between January 2015 and June 2021, 1168 patients undergoing dialysis with CAD were assessed from 30 tertiary medical centers. The primary outcome was all-cause death, and the secondary outcome was cardiovascular death. Inverse probability of treatment weighting (IPTW) and propensity score matching (PSM) were performed to account for between-group differences.

RESULTS

Overall, ACEI or ARB were prescribed to 518 patients (44.3%) upon discharge. After a median follow-up of 22.2 months, 361 (30.9%) patients died, including 243 cardiovascular deaths. The use of ACEI or ARB was associated with a significantly lower risk of all-cause (25.3% vs 35.4%, hazard ratio [HR] 0.65, 95% confidence interval [CI] 0.52-0.82, p < 0.001) and cardiovascular death (17.0% vs 23.8%; HR 0.64, 95% CI 0.48-0.83, p = 0.001). These findings remained consistent across IPTW and PSM analyses. Sensitivity analyses for ACEI and ARB use separately yielded similar results.

CONCLUSIONS

Our findings suggested that among patients undergoing dialysis with CAD, ACEI or ARB use was associated with a lower risk of all-cause and cardiovascular death.

Predicting susceptibility to COVID-19 infection in patients on maintenance hemodialysis by cross-coupling soluble ACE2 concentration with lymphocyte count: an algorithmic approach

Introduction

Patients on maintenance hemodialysis (MHD) were more vulnerable to and had a higher mortality during the COVID-19 pandemic. As angiotensin converting enzyme 2 (ACE2) and transmembrane protease serine S1 member 2 (TMPRSS2) played crucial roles in viral entry into the human host cells, we therefore investigated in the MHD patients whether their plasma levels were associated with susceptibility to the COVID-19.

Methods

Blood samples were collected from the patients in our then COVID-19 free center immediately upon lifting of the stringent quarantine measures in early December of 2022 and infection situation was observed within the following 2 weeks. Plasma levels of the soluble ACE2 (sACE2), ACE (sACE) and TMPRSS2 (sTMPRSS2) were measured with ELISA method. Data were stepwisely tested for independent effect, relevant role and synergistic action on the susceptibility by multiple logistic regression, receiver operating characteristic curve and multiple dimensionality reduction (MDR) method, respectively.

Results

Among the 174 eligible patients, 95 (54.6%) turned COVID-19 positive with a male to female ratio of 1.57 during the observation period. Comparing with the uninfected, the infected had significantly higher sACE2 and lower sTMPRSS2 levels upon comparable sACE concentration. Besides the sACE2, factors associated with susceptibility were vintage and individual session time of the hemodialysis, smoking and comorbidity of hepatitis, whereas lymphocyte counts showed a tendency (p = 0.052). Patients simultaneously manifesting higher sACE2 level and lower lymphocyte counts had an increased infection risk as confirmed by the MDR method.

Conclusion

By sorting out the susceptible ones expeditiously, this algorithmic approach may help the otherwise vulnerable MHD patients weather over future wave of COVID-19 variants or outbreak of other viral diseases.

Inhibition of endoplasmic reticulum stress restores the balance of renal RAS components and lowers blood pressure in the spontaneously hypertensive rats

BACKGROUND

Endoplasmic reticulum (ER) stress has been shown to play a critical role in the pathogenesis of hypertension. However, the underlying mechanisms for lowering blood pressure (BP) by suppressing ER stress remain unclear. Here, we hypothesized that inhibition of ER stress could restore the balance between RAS components and lower BP in spontaneously hypertensive rats (SHRs).

METHODS

Wistar-Kyoto (WKY) rats and SHRs received vehicle or 4-PBA, an ER stress inhibitor, in the drinking water for 4 weeks. BP was measured by tail-cuff plethysmography, and the expression of RAS components was examined by Western blot.

RESULTS

Compared with vehicle-treated WKY rats, vehicle-treated SHRs exhibited higher blood pressure and increased renal ER stress and oxidative stress, accompanied by impaired diuresis and natriuresis. Moreover, SHRs had higher ACE and AT₁R and lower AT₂R, ACE2, and MasR expressions in the kidney. Interestingly, 4-PBA treatment improved impaired diuresis and natriuresis and lowered blood pressure in SHRs, accompanied by reducing ACE and AT₁R protein expression and increasing AT₂R, ACE2, and MasR expression in the kidneys of SHRs. In addition, these changes were associated with the reduction of ER stress and oxidative stress.

CONCLUSIONS

These results suggest that the imbalance of renal RAS components was associated with increased ER stress in SHRs. Inhibition of ER stress with 4-PBA reversed the imbalance of renal RAS components and restored the impaired diuresis and natriuresis, which, at least in part, explains the blood pressure-lowering effects of 4-PBA in hypertension.

Association of Renin-Angiotensin System Blockers with Survival in Patients on Maintenance Hemodialysis

Additional studies are needed to confirm whether the use of renin-angiotensin system blockers (RASBs) induces survival benefits in patients on hemodialysis (HD). This study aimed to evaluate patient survival with the use of RASBs in a large sample of maintenance HD patients. This study used data from the national HD quality assessment program and claim data from South Korea (n = 54,903). A patient using RASBs was defined as someone who had received more than one prescription during the 6 months of each HD quality assessment period. The patients were divided into three groups as follows: Group 1, no prescription for anti-hypertensive drugs; Group 2, prescription for anti-hypertensive drugs other than RASBs; and Group 3, prescription for RASBs. The five-year survival rates in Groups 1, 2, and 3 were 72.1%, 64.5%, and 66.6%, respectively (p < 0.001 for Group 1 vs. Group 2 or 3; p = 0.001 for Group 2 vs. Group 3). Group 1 had the highest patient survival rates among the three groups, and Group 3 had higher patient survival rates compared to Group 2. Group 3 had higher patient survival rates than Group 2; however, the difference in patient survival rates between Group 2 and Group 3 was relatively small. Multivariate Cox regression analyses showed similar trends as those of univariate analyses. The highest survival rates from our study were those of patients who had not used anti-hypertensive drugs. Between patients treated with RASBs and those with other anti-hypertensive drugs, patient survival rates were higher in patients treated with RASBs.

The Surging Mechanistic Role of Angiotensin Converting Enzyme 2 in Human Pathologies: A Potential Approach for Herbal Therapeutics

Advancements in biological sciences revealed the significant role of angiotensin-converting enzyme 2 (ACE2), a key cell surface receptor in various human pathologies. ACE2 is a metalloproteinase that not only functions in the regulation of Angiotensin II but also possesses some non-catalytic roles in the human body. There is considerable uncertainty regarding its protein expression, despite its presence in virtually all organs. The level of ACE2 expression and its subcellular localisation in humans may be a key determinant of susceptibility to various infections, symptoms, and outcomes of numerous diseases. Therefore, we summarize the distribution and expression pattern of ACE2 in different cell types related to all major human tissues and organs. Moreover, this review constitutes accumulated evidences of the important resources for further studies on ACE2 Inhibitory capacity via different natural compounds in order to understand its mechanism as the potential drug target in disease pathophysiology and to aid in the development of an effective therapeutic approach towards the various diseases.

Correlation between Angiotensin Serum Levels and Very-Low-Frequency Spectral Power of Heart Rate Variability during Hemodialysis

Cardiovascular regulatory mechanisms that fail to compensate for ultrafiltration and cause hypovolemia during hemodialysis (HD) are not completely understood. This includes the interaction between the autonomic nervous system and the biochemistry that regulates blood pressure and modulates cardiac activity and vascular tone in response to hypovolemia in patients treated with HD. The objective was to evaluate the association of spectral indices of heart rate variability (HRV) with serum levels of angiotensin II, angiotensin 1–7, nitric oxide and total antioxidant capacity during HD. Electrocardiographic records were obtained from 20 patients during HD (3 h), from which HRV data and spectral power data in the very-low-frequency (VLF), low-frequency (LF) and high-frequency (HF) bands were generated. Three blood samples per patient were collected during HD (0.0, 1.5, 3.0 h) to determine the levels of biomarkers involved in the pressor response during HD. Angiotensin II had a positive correlation with VLF (r = 0.390) and with LF/HF (r = 0.359) and a negative correlation with LF (r = −0.262) and HF (r = −0.383). There were no significant correlations between HRV and the other biomarkers. These results suggest that during HD, VLF could reflect the serum levels of angiotensin II, which may be associated with the autonomic response to HD.

Higher Soluble ACE2 Levels and Increased Risk of Infection-Related Hospitalization in Patients on Maintenance Hemodialysis

Background

Angiotensin-converting enzyme 2 (ACE2) works as an endogenous counter-regulator of the renin-angiotensin system, which has pivotal roles in preventing both cardiovascular disease (CVD) and inflammation. In general populations, higher plasma soluble ACE2 levels were reported to be associated with increased risks of all-cause death and major CVD. Because infections are fatal in patients on maintenance hemodialysis, we aimed to explore whether soluble ACE2 levels are associated with an increased risk of infection-related hospitalization in these patients.

Methods

Using data from a prospective, multicenter, cohort study conducted in Tokyo, Japan, we performed a post-hoc analyses of 724 clinically stable patients on maintenance hemodialysis. We measured baseline serum soluble ACE2 levels and assessed potential determinants of its with infection-related hospitalization as a primary outcome as well as all-cause death and CVD as secondary outcomes using a Cox proportional hazards model.

Results

The soluble ACE2 level (median, 0.16 ng/ml; interquartile range, 0.07–0.57 ng/ml) showed a weak negative association with age. During a median follow-up of 39 months, 106 patients (14.6%) were hospitalized with infectious diseases. Compared with the lower half of soluble ACE2 levels, the higher half was associated with an increased risk of infection-related hospitalization (hazard ratio, 1.57; 95% confidence interval, 1.02–2.41) with adjustment by other risk factors. On the other hand, there were no significant associations between soluble ACE2 and risks of all-cause death and CVD.

Conclusion

Higher soluble ACE2 levels may associate with an increased risk of infection-related hospitalization in patients on maintenance hemodialysis.

Possible benefits of exogenous melatonin for individuals on dialysis: a narrative review on potential mechanisms and clinical implications

Prevention of oxidative stress and inflammation in chronic kidney disease patients (CKD) on dialysis may reduce dialysis-associated complications. Administration of powerful antioxidants may improve the consequences of peritoneal dialysis (PD) and hemodialysis (HD). This narrative review aimed to show the potential therapeutic effects of melatonin (MLT) on the consequences of CKD patients receiving HD or PD. The results of preclinical and clinical studies have proven that CKD and dialysis are accompanied by reduced endogenous MLT levels and related complications such as sleep disorders. Enhanced oxidative stress, inflammation, cellular damages, and renal fibrosis, along with dysregulation of the renin-angiotensin system (RAS), have been observed in CKD and patients on dialysis. Results of studies have revealed that the restoration of MLT via the exogenous source may regulate oxidative stress, inflammation, and RAS functions, inhibit fibrosis, and improve complications in patients with long-term dialysis patients. In summary, treatment of patients with CKD and dialysis with exogenous MLT is suggested as a practical approach in reducing the outcomes and improving the quality of life in patients via antioxidant, anti-inflammatory, and anti-fibrotic signaling pathways. Therefore, this hormone can be considered in clinical practice to manage dialysis-related complications.

Aberrant NLRP3 Inflammasome Activation Ignites the Fire of Inflammation in Neuromuscular Diseases

Inflammasomes are molecular hubs that are assembled and activated by a host in response to various microbial and non-microbial stimuli and play a pivotal role in maintaining tissue homeostasis. The NLRP3 is a highly promiscuous inflammasome that is activated by a wide variety of sterile triggers, including misfolded protein aggregates, and drives chronic inflammation via caspase-1-mediated proteolytic cleavage and secretion of proinflammatory cytokines, interleukin-1β and interleukin-18. These cytokines further amplify inflammatory responses by activating various signaling cascades, leading to the recruitment of immune cells and overproduction of proinflammatory cytokines and chemokines, resulting in a vicious cycle of chronic inflammation and tissue damage. Neuromuscular diseases are a heterogeneous group of muscle disorders that involve injury or dysfunction of peripheral nerves, neuromuscular junctions and muscles. A growing body of evidence suggests that dysregulation, impairment or aberrant NLRP3 inflammasome signaling leads to the initiation and exacerbation of pathological processes associated with neuromuscular diseases. In this review, we summarize the available knowledge about the NLRP3 inflammasome in neuromuscular diseases that affect the peripheral nervous system and amyotrophic lateral sclerosis, which affects the central nervous system. In addition, we also examine whether therapeutic targeting of the NLRP3 inflammasome components is a viable approach to alleviating the detrimental phenotype of neuromuscular diseases and improving clinical outcomes.

Measured sodium excretion is associated with CKD progression: results from the KNOW-CKD study

BACKGROUND

Diet is a modifiable factor of chronic kidney disease (CKD) progression. However, the effect of dietary salt intake on CKD progression remains unclear. Therefore, we analyzed the effect of dietary salt intake on renal outcome in Korean patients with CKD.

METHODS

We measured 24-h urinary sodium (Na) excretion as a marker of dietary salt intake in the prospective, multi-center, longitudinal KoreaN cohort study for Outcome in patients With CKD (KNOW-CKD). Data were analyzed from CKD patients at Stages G3a to G5 (n = 1254). We investigated the association between dietary salt intake and CKD progression. Patients were divided into four quartiles of dietary salt intake, which was assessed using measured 24-h urinary Na excretion. The study endpoint was composite renal outcome, which was defined as either halving the estimated glomerular filtration rate or developing end-stage renal disease.

RESULTS

During a median (interquartile range) follow-up of 4.3 (2.8-5.8) years, 480 (38.7%) patients developed the composite renal event. Compared with the reference group (Q2, urinary Na excretion: 104.2 ≤ Na excretion < 145.1 mEq/day), the highest quartile of measured 24-h urinary Na excretion was associated with risk of composite renal outcome [Q4, urinary Na excretion ≥192.9 mEq/day, hazard ratio 1.8 (95% confidence interval 1.12-2.88); P = 0.015] in a multivariable hazards model. Subgroup analyses showed that high-salt intake was particularly associated with a higher risk of composite renal outcome in women, in patients <60 years of age, in those with uncontrolled hypertension and in those with obesity.

CONCLUSIONS

High salt intake was associated with increased risk of progression in CKD.

End-Stage Renal Disease Patients on Chronic Hemodialysis Fare Better With COVID-19: A Retrospective Cohort Study From the New York Metropolitan Region

Introduction

Several comorbid conditions have been identified as risk factors in patients with coronavirus disease 2019 (COVID-19). However, there is a dearth of data describing the impact of COVID-19 infection in patients with end-stage renal disease on hemodialysis (ESRD-HD).

Methods

This retrospective case series analyzed 362 adult patients consecutively hospitalized with confirmed COVID-19 illness between March 12, 2020, and May 13, 2020, at a teaching hospital in the New York City metropolitan area. The primary outcome was severe pneumonia as defined by the World Health Organization. Secondary outcomes were the (1) the Combined Outcome of Acute respiratory distress syndrome or in-hospital Death (COAD), and (2) need for high levels of oxygen supplementation (HiO₂).

Results

Patients with ESRD-HD had lower odds for poor outcomes including severe pneumonia [odds ratio (OR) 0.4, confidence interval (CI) 0.2-0.9, p=.04], HiO₂ [OR 0.3, CI (0.1-0.8), p=.02] and COAD [OR 0.4, CI (0.2-1.05), p=.06], when compared to patients without ESRD. In contrast, higher odds for severe pneumonia, COAD and HiO₂ were seen with advancing age. African Americans were over-represented in the hospitalized patient cohort, when compared to their representation in the community (35% vs 18%). Hispanics had higher odds for severe illness and HiO₂ when compared to Caucasians.

Conclusions

Patients with ESRD-HD had a milder course of illness with a lower likelihood of severe pneumonia and a lesser need for aggressive oxygen supplementation when compared to patients not on chronic dialysis. The lower odds of severe illness in ESRD-HD patients might have a pathophysiologic basis and need to be further explored.

The CX3CL1/CX3CR1 axis is upregulated in chronic kidney disease and contributes to angiotensin II-induced migration of vascular smooth muscle cells

BACKGROUND

The role of the chemokine axis, CX3CL1/CX3CR1, in the development of cardiovascular diseases has been widely speculated. Angiotensin II (Ang II) is a pivotal factor promoting cardiovascular complications in patients with chronic kidney disease (CKD). Whether there is a link between the two in CKD remains unclear.

METHODS

The uremic mice were treated with losartan for 8 weeks, and the expression of aortic CX3CL1/CX3CR1 was detected. Cultured mouse aortic vascular smooth muscle cells (VSMCs) were stimulated with Ang II, and then CX3CR1 expression was assessed by western blot. After the targeted disruption of CX3CR1 by transfection with siRNA, the migration of VSMCs was detected by transwell assay. Finally, both the activation of Akt pathway and the expression of IL-6 were detected by western blot.

RESULTS

Losartan treatment reduced the upregulation of aortic CX3CL1/CX3CR1 expression in uremic mice. In vitro, Ang II significantly upregulated CX3CR1 expression in VSMCs. Targeted disruption of CX3CR1 attenuated Ang II-induced migration of VSMCs. In addition, the use of CX3CR1-siRNA suppressed Akt phosphorylation and IL-6 production in VSMCs stimulated by Ang II.

CONCLUSIONS

The aortic CX3CL1/CX3CR1 is upregulated by Ang II in CKD, and it contributes to Ang II-induced migration of VSMCs in vitro.

Imbalanced plasma ACE and ACE2 level in the uremic patients with cardiovascular diseases and its change during a single hemodialysis session

Background: The renin-angiotensin system (RAS) has significant influences on heart and renal disease progression. Angiotensin converting enzyme (ACE) and angiotensin converting enzyme II (ACE2) are major peptidases of RAS components and play counteracting functions through angiotensin II (Ang II)/ATIR and angiotensin-(1–7) (Ang-(1–7))/Mas axis, respectively.

Methods: There were 360 uremic patients on regular hemodialysis (HD) treatment (inclusive of 119 HD patients with cardiovascular diseases (CVD) and 241 HD patients without CVD and 50 healthy subjects were enrolled in this study. Plasma ACE, ACE2, Ang II and Ang-(1–7) levels of the HD patients were determined.

Results: We compared pre-HD levels of plasma ACE, ACE2, Ang II and Ang-(1–7) in the HD patients with and without CVD to those of the controls. The HD patients, particularly those with CVD, showed a significant increase in the levels of ACE and Ang II, whereas ACE2 and Ang-(1–7) levels were lower than those in the healthy controls. Therefore, imbalanced ACE/ACE2 was observed in the HD patients with CVD. In the course of a single HD session, the plasma ACE, ACE/ACE2 and Ang II levels in the HD patients with CVD were increased from pre-HD to post-HD. On the contrary, ACE2 levels were decreased after the HD session. These changes were not detected in the HD patients without CVD.

Conclusions: Pathogenically imbalanced circulating ACE/ACE2 was detected in the HD patients, particularly those with CVD. HD session could increase ACE/Ang II/AT1R axis and decrease ACE2/Ang-(1–7)/Mas axis activity in the circulation of HD patients with CVD.

Erythropoietin mediates brain-vascular-kidney crosstalk and may be a treatment target for pulmonary and resistant essential hypertension

Organ crosstalk pathways represent the next frontier for target-mining in molecular medicine for existing syndromes. Pulmonary hypertension and resistant essential hypertension are syndromes that have been proven elusive in etiology, and frequently refractory to first-line management. Underlying crosstalk mechanisms, not yet considered in these treatments, may hinder outcomes or unlock novel treatments. This review focuses systematically on erythropoietin, a synthesizable molecule, as a mediator of brain-kidney crosstalk. Insights gained from this review will be applied to cardiovascular diseases in a clinician-directed fashion.

Renoprotective Effect of Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers in Diabetic Patients with Proteinuria

BACKGROUND/AIMS

Limited evidence exists on the choice of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) in diabetic patients with nephropathy. We aim to assess the renal effectiveness and safety of these drugs among diabetic nephropathy patients.

METHODS

This retrospective cohort study was conducted with diabetic nephropathy patients who initiated ACEI or ARB monotherapy. The primary outcome was a composite of end stage of renal disease and renal transplantation, and the secondary outcome was all-cause mortality. The safety endpoint was hyperkalemia.

RESULTS

Three thousand seven hundred and thirty-nine ACEI users and 3,316 ARB users were identified. ARBs seemed to be inferior to ACEIs given their poorer renal outcome (HR 1.31; 95% CI, 1.15-1.50) and higher risk of hyperkalemia (HR 1.17; 95% CI, 1.04-1.32). Among the four ACEIs compared, captopril was an inferior treatment choice given its poorer renal outcomes (HR 1.42; 95% CI, 1.05-1.93) and higher mortality rate (HR 1.25; 95% CI, 1.01-1.55). Irbesartan appeared to be a poorer treatment choice among the three ARBs compared, given its inferior renal protective effect (HR 1.35; 95% CI, 1.03-1.78).

CONCLUSIONS

Our findings suggest ACEIs as a relatively more renoprotective and safer treatment as compared to ARBs. Captopril and irbesartan may be inferior to the other ACEIs and ARBs respectively.

Significance of angiotensin 1-7 coupling with MAS1 receptor and other GPCRs to the renin-angiotensin system: IUPHAR Review 22

Angiotensins are a group of hormonal peptides and include angiotensin II and angiotensin 1-7 produced by the renin angiotensin system. The biology, pharmacology and biochemistry of the receptors for angiotensins were extensively reviewed recently. In the review, the receptor nomenclature committee was not emphatic on designating MAS1 as the angiotensin 1-7 receptor on the basis of lack of classical G protein signalling and desensitization in response to angiotensin 1-7, as well as a lack of consensus on confirmatory ligand pharmacological analyses. A review of recent publications (2013-2016) on the rapidly progressing research on angiotensin 1-7 revealed that MAS1 and two additional receptors can function as 'angiotensin 1-7 receptors', and this deserves further consideration. In this review we have summarized the information on angiotensin 1-7 receptors and their crosstalk with classical angiotensin II receptors in the context of the functions of the renin angiotensin system. It was concluded that the receptors for angiotensin II and angiotensin 1-7 make up a sophisticated cross-regulated signalling network that modulates the endogenous protective and pathogenic facets of the renin angiotensin system.