HIF Activation Against CVD in CKD: Novel Treatment Opportunities

Daprodustat for Post-Transplant Anemia in Renal Transplant Recipients

BACKGROUND

Daprodustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, has been reported to be effective in treating conservative renal failure and renal anemia in patients undergoing dialysis. However, its effects on post-transplant anemia have not yet been reported. This study aimed to determine whether daprodustat may be a useful treatment for post-transplant anemia.

MATERIALS

Excluding 5 cases in which the drug was discontinued due to side effects, 21 post-transplant patients treated with daprodustat for ≥12 months and available for follow-up were analyzed. Changes in hemoglobin levels, iron metabolism, estimated glomerular filtration rate, and low-density lipoprotein levels were evaluated over 1 year.

RESULTS

The average hemoglobin level was 10.1 g/dL before treatment, and after 1, 2, 3, 6, 9, and 12 months, these had increased significantly to 10.9, 11.2, 11.9, 12.3, 12.3, and 12.6, respectively. Ferritin levels were significantly lower throughout the 12-month study period. Transferrin saturation was significantly lower than before treatment during the first 6 months, with no significant differences after that. The participants' estimated glomerular filtration rate and low-density lipoprotein cholesterol levels did not change significantly throughout the treatment.

CONCLUSION

Daprodustat significantly increased hemoglobin levels was easily dose-adjusted and was relatively safe for continuous use over 1 year. It was also effective in patients who had responded inadequately to erythropoiesis-stimulating agents. Therefore, we conclude that daprodustat may be a useful treatment for post-transplant anemia.

Higher hemoglobin levels using darbepoetin alfa and kidney outcomes in advanced chronic kidney disease without diabetes: a prespecified secondary analysis of the PREDICT trial

BACKGROUND

In the primary analysis of the PREDICT trial, a higher hemoglobin target (11-13 g/dl) with darbepoetin alfa did not improve renal outcomes compared with a lower hemoglobin target (9-11 g/dl) in advanced chronic kidney disease (CKD) without diabetes. Prespecified secondary analyses were performed to further study the effects of targeting higher hemoglobin levels on renal outcomes.

METHODS

Patients with an estimated glomerular filtration rate (eGFR) 8-20 ml/min/1.73 m2 without diabetes were randomly assigned 1:1 to the high- and low-hemoglobin groups. The differences between the groups were evaluated for the following endpoints and cohort sets: eGFR and proteinuria slopes, assessed using a mixed-effects model in the full analysis set and the per-protocol set that excluded patients with off-target hemoglobin levels; the primary endpoint of composite renal outcome, evaluated in the per-protocol set using the Cox model.

RESULTS

In the full analysis set (high hemoglobin, n = 239; low hemoglobin, n = 240), eGFR and proteinuria slopes were not significantly different between the groups. In the per-protocol set (high hemoglobin, n = 136; low hemoglobin, n = 171), the high-hemoglobin group was associated with reduced composite renal outcome (adjusted hazard ratio: 0.64; 95% confidence interval: 0.43-0.96) and an improved eGFR slope (coefficient: + 1.00 ml/min/1.73 m2/year; 95% confidence interval: 0.38-1.63), while the proteinuria slope did not differ between the groups.

CONCLUSIONS

In the per-protocol set, the high-hemoglobin group demonstrated better kidney outcomes than the low-hemoglobin group, suggesting a potential benefit of maintaining higher hemoglobin levels in patients with advanced CKD without diabetes.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov (identifier: NCT01581073).

Disturbance of Hypoxia Response and Its Implications in Kidney Diseases

Significance: The disturbance of the hypoxia response system is closely related to human diseases, because it is essential for the maintenance of homeostasis. Given the significant role of the hypoxia response system in human health, therapeutic applications targeting prolyl hydroxylase-hypoxia-inducible factor (HIF) signaling have been attempted. Thus, systemically reviewing the hypoxia response-based therapeutic strategies is of great significance. Recent Advances: Disturbance of the hypoxia response is a characteristic feature of various diseases. Targeting the hypoxia response system is, thus, a promising therapeutic strategy. Interestingly, several compounds and drugs are currently under clinical trials, and some have already been approved for use in the treatment of certain human diseases. Critical Issues: We summarize the molecular mechanisms of the hypoxia response system and address the potential therapeutic implications in kidney diseases. Given that the effects of hypoxia response in kidney diseases are likely to depend on the pathological context, specific cell types, and the differences in the activation pattern of HIF isoforms, the precise application is critical for the treatment of kidney diseases. Although HIF-PHIs (HIF-PHD inhibitors) have been proven to be effective and well tolerated in chronic kidney disease patients with anemia, the potential on-target consequence of HIF activation and some outstanding questions warrant further consideration. Future Direction: The mechanism of the hypoxia response system disturbance remains unclear. Elucidation of the molecular mechanism of hypoxia response and its precise effects on kidney diseases warrants clarification. Considering the complexity of the hypoxia response system and multiple biological processes controlled by HIF signaling, the development of more specific inhibitors is highly warranted. Antioxid. Redox Signal. 37, 936-955.

Molecular basis and clinical implications of HIFs in cardiovascular diseases

Oxygen maintains the homeostasis of an organism in a delicate balance in different tissues and organs. Under hypoxic conditions, hypoxia-inducible factors (HIFs) are specific and dominant factors in the spatiotemporal regulation of oxygen homeostasis. As the most basic functional unit of the heart at the cellular level, the cardiomyocyte relies on oxygen and nutrients delivered by the microvasculature to keep the heart functioning properly. Under hypoxic stress, HIFs are involved in acute and chronic myocardial pathology because of their spatiotemporal specificity, thus granting them therapeutic potential. Most adult animals lack the ability to regenerate their myocardium entirely following injury, and complete regeneration has long been a goal of clinical treatment for heart failure. The precise manipulation of HIFs (considering their dynamic balance and transformation) and the development of HIF-targeted drugs is therefore an extremely attractive cardioprotective therapy for protecting against myocardial ischemic and hypoxic injury, avoiding myocardial remodeling and heart failure, and promoting recovery of cardiac function.

Hypoxia-inducible factor prolyl hydroxylase enzyme inhibitors: ready for primetime?

PURPOSE OF REVIEW

Hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitors have recently been developed as a new treatment for anemia associated with chronic kidney disease (CKD). Several of these have been approved in Europe (roxadustat), China, and Japan, but none approved in the United States to date, although daprodustat has been submitted as a new drug application to the Food and Drug Administration. The aim of this review is to critically appraise the available data, particularly the most recent publications, and offer a personal viewpoint on whether or not these drugs are ready for primetime.

RECENT FINDINGS

The efficacy of HIF prolyl hydroxylase inhibitors in improving CKD anemia and maintaining a higher hemoglobin is undisputed, but there remain some concerns about safety, particularly in the long term. Some of the safety concerns may result from an exaggerated pharmacological response, while other potential adverse effects could be due to transcriptional effects of these agents beyond genes involved in erythropoiesis.

SUMMARY

HIF prolyl hydroxylase inhibitors are already being used in clinical practice in several countries of the world, and ongoing research is being conducted to define the role of these drugs not only in the management of anemia but also beyond into other clinical settings.

Left Heart Failure Caused by Capacity Overload in Peritoneal Dialysis Patients

Background

This study sets out to investigate the incidence of acute left ventricular failure in peritoneal dialysis patients with different volume loads and to analyze the related risk factors for LVF in these patients.

Methods

This study involved patients who received peritoneal dialysis in our hospital between September 2018 and January 2021. The demographic data and biochemical indicators of the patients were collected. The bioimpedance analysis method was used to determine the volume overload [overhydration (OH)] level of patients, and cardiac color Doppler ultrasound was used to detect changes in their cardiac structure. According to the LVF diagnostic criteria of symptoms and laboratory tests, the patients were divided into the LVF and non-LVF groups and then divided according to their OH level into the normal volume (OH ≤1.1 L) and volume overload (OH >1.1 L) groups. The incidence of LVF in was analyzed in patients with different volume loads, and logistic regression was used to identify the risk factors for LVF.

Results

Among the 226 peritoneal dialysis patients enrolled in this study, 125 patients (55.3%) had LVF. The normal volume group (n = 68, 30.1%) included 22 patients (32.4%) with LVF, and the volume overload group (n = 158, 69.9%) included 84 patients (53.2%) with LVF. In the volume overload group, 74 patients (46.8%) had subclinical volume overload, including 35 patients (47.3%) with LVF, and 84 patients (53.2%) had clinical volume overload, including 65 patients (77.4%) LVF. Multivariate logistic regression analysis revealed a high OH level (OR = 1.862, 95% CI: 1.353-2.668, P < 0.001) and low hemoglobin level (OR = 0.845, 95% CI: 0.721-0.980, P = 0.008) to be independent risk factors for LVF.

Conclusions

LVF has a high incidence in peritoneal dialysis patients, especially those with volume overload. A high OH level and low hemoglobin level are independent risk factors for LVF.

Roxadustat Attenuates the Disruption of Epithelial Tight Junction in Caco2 Cells and a Rat Model of CKD Through MicroRNA-223

Introduction

Increasing evidence supports the idea that the disruption of epithelial tight junction proteins (TJPs) caused by accumulation of uremia toxins, such as homocysteine (Hcy), is one of the most important mechanisms underlying the damage of intestinal barrier function (IBF) in chronic kidney disease (CKD). Since the decrease of hypoxia inducible factor-1α (HIF-1α) is reported to be involved in Hcy-induced cell injury, and the upregulation of microRNA-223 (miR-223) plays a vital protective role in the impairment of IBF in the experimental colitis, we investigated the effect of HIF-1α stabilizer roxadustat on the disruption of TJPs induced by Hcy and CKD and the underlying mechanism.

Methods

Chronic kidney disease was induced in rats via 5/6 nephrectomy. In a series of experiments, the rats were treated orally with roxadustat of different doses. The expression of tight junction proteins, HIF-1α, and miR-223 was analyzed in different groups by western blotting analysis, RT-qPCR techniques and immunofluorescence. A series of experiments with cultured Caco2 cells was performed.

Results

The results showed that the expression of TJPs (occludin, claudin-1, and ZO-1) decreased significantly, accompanied by the reduction of HIF-1α and miR-223 in Hcy-treated Caco2 cells and colonic mucosa of uremic rats. The reduction of HIF-1α and miR-223 was reversed by roxadustat and the decrease of TJPs expression was attenuated in both Caco2 cells induced by Hcy and colon tissue of CKD rats. Furthermore, transfection with miR-223 mimics increased the expression of TJPs, while transfection with miR-223 inhibitor decreased their expression in Caco2 cells. MiR-223 inhibitor applied before roxadustat treatment partly diminished the effect of roxadustat on TJPs expression in Caco2 cells.

Conclusion

These results indicated that roxadustat attenuated the disruption of epithelial TJPs induced by Hcy in Caco2 cells and the damage of colonic epithelium in CKD rats through the upregulation of miR-223 induced by HIF-1α. A novel insight into the IBF dysfunction in CKD was provided, and it suggests a potential therapeutic use of roxadustat for the IBF dysfunction besides anemia in CKD.

Effects of Roxadustat on Erythropoietin Production in the Rat Body

Anemia is a major complication of chronic renal failure. To treat this anemia, prolylhydroxylase domain enzyme (PHD) inhibitors as well as erythropoiesis-stimulating agents (ESAs) have been used. Although PHD inhibitors rapidly stimulate erythropoietin (Epo) production, the precise sites of Epo production following the administration of these drugs have not been identified. We developed a novel method for the detection of the Epo protein that employs deglycosylation-coupled Western blotting. With protein deglycosylation, tissue Epo contents can be quantified over an extremely wide range. Using this method, we examined the effects of the PHD inhibitor, Roxadustat (ROX), and severe hypoxia on Epo production in various tissues in rats. We observed that ROX increased Epo mRNA expression in both the kidneys and liver. However, Epo protein was detected in the kidneys but not in the liver. Epo protein was also detected in the salivary glands, spleen, epididymis and ovaries. However, both PHD inhibitors (ROX) and severe hypoxia increased the Epo protein abundance only in the kidneys. These data show that, while Epo is produced in many tissues, PHD inhibitors as well as severe hypoxia regulate Epo production only in the kidneys.

Physiology and Inflammation Driven Pathophysiology of Iron Homeostasis-Mechanistic Insights into Anemia of Inflammation and Its Treatment

Anemia is very common in patients with inflammatory disorders. Its prevalence is associated with severity of the underlying disease, and it negatively affects quality of life and cardio-vascular performance of patients. Anemia of inflammation (AI) is caused by disturbances of iron metabolism resulting in iron retention within macrophages, a reduced erythrocyte half-life, and cytokine mediated inhibition of erythropoietin function and erythroid progenitor cell differentiation. AI is mostly mild to moderate, normochromic and normocytic, and characterized by low circulating iron, but normal and increased levels of the storage protein ferritin and the iron hormone hepcidin. The primary therapeutic approach for AI is treatment of the underlying inflammatory disease which mostly results in normalization of hemoglobin levels over time unless other pathologies such as vitamin deficiencies, true iron deficiency on the basis of bleeding episodes, or renal insufficiency are present. If the underlying disease and/or anemia are not resolved, iron supplementation therapy and/or treatment with erythropoietin stimulating agents may be considered whereas blood transfusions are an emergency treatment for life-threatening anemia. New treatments with hepcidin-modifying strategies and stabilizers of hypoxia inducible factors emerge but their therapeutic efficacy for treatment of AI in ill patients needs to be evaluated in clinical trials.

Atherosclerotic Vascular Disease Associated with Chronic Kidney Disease

Cardiovascular risk increases as glomerular filtration rate (GFR) declines in progressive renal disease and is maximal in patients with end-stage renal disease requiring maintenance dialysis. Atherosclerotic vascular disease, for which hyperlipidemia is the main risk factor and lipid-lowering therapy is the key intervention, is common. However, the pattern of dyslipidemia changes with low GFR and the association with vascular events becomes less clear. While the pathophysiology and management of patients with early chronic kidney disease (CKD) is similar to the general population, advanced and end-stage CKD is characterized by a disproportionate increase in fatal events, ineffectiveness of statin therapy, and greatly increased risk associated with coronary interventions. The most effective strategies to reduce atherosclerotic cardiovascular disease in CKD are to slow the decline in renal function or to restore renal function by transplantation.

Hypoxia-Inducible Factor Stabilization as an Emerging Therapy for CKD-Related Anemia: Report From a Scientific Workshop Sponsored by the National Kidney Foundation

The National Kidney Foundation convened an interdisciplinary international workshop in March 2019 to discuss the potential role of a new class of agents for the treatment of anemia in patients with chronic kidney disease (CKD): the hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs). International experts with expertise in physiology, biochemistry, structural chemistry, translational medicine and clinical management of anemia participated. Participants reviewed the unmet needs of current anemia treatment, the biology of hypoxia-inducible factor, the pharmacology of prolyl hydroxylase inhibitors, and the results of phase 2 clinical trials of HIF-PHIs among patients with both non-dialysis dependent and dialysis-dependent CKD. The results of key phase 3 clinical trials of HIF-PHIs in the public domain as of this writing are also presented in this article although they appeared after the workshop was completed. Participants in the workshop developed a number of recommendations for further examination of HIF-PHIs which are summarized in this article and include long-term safety issues, potential benefits, and practical considerations for implementation including patient and provider education.

Cardiovascular safety and efficacy of vadadustat for the treatment of anemia in non-dialysis-dependent CKD: Design and baseline characteristics

Current clinical practice guidelines for anemia management in non-dialysis-dependent chronic kidney disease (NDD-CKD) recommend the use of erythropoiesis-stimulating agents (ESAs) as standard of care. Vadadustat, an investigational oral hypoxia-inducible factor prolyl-hydroxylase inhibitor, stimulates endogenous erythropoietin production. The PRO₂TECT program comprises 2 global, Phase 3, randomized, open-label, active-controlled, sponsor-blind clinical trials to evaluate safety and efficacy of vadadustat vs darbepoetin alfa in adult patients with anemia associated with NDD-CKD. Patients recruited into the ESA-untreated NDD-CKD trial (N = 1751) had hemoglobin <10 g/dL and had not received an ESA within 8 weeks prior to inclusion in the study. Patients recruited into the ESA-treated NDD-CKD trial (N = 1725) had hemoglobin between 8 and 11 g/dL (US) or 9 and 12 g/dL (non-US) and were actively treated with an ESA for anemia associated with CKD. Trial periods in both trials include (1) correction/conversion (weeks 0-23); (2) maintenance (weeks 24-52); (3) long-term treatment (week 53 to end of treatment); and (4) safety follow-up (end-of-treatment to 4 weeks later). The primary safety endpoint is time to first adjudicated major adverse cardiovascular event, defined as all-cause mortality, nonfatal myocardial infarction, or nonfatal stroke, pooled across both trials. The primary efficacy endpoint in each trial is change in hemoglobin from baseline to primary evaluation period (weeks 24-36), comparing vadadustat vs darbepoetin alfa treatment groups. Demographics and baseline characteristics are similar among patients in both trials and broadly representative of the NDD-CKD population. These trials will help to evaluate the safety and efficacy of vadadustat for management of anemia associated with NDD-CKD.

HIF in Nephrotoxicity during Cisplatin Chemotherapy: Regulation, Function and Therapeutic Potential

Simple Summary

Cisplatin is a widely used chemotherapy drug, but its use and efficacy are limited by its nephrotoxicity. HIF has protective effects against kidney injury during cisplatin chemotherapy, but it may attenuate the anti-cancer effect of cisplatin. In this review, we describe the role and regulation of HIF in cisplatin-induced nephrotoxicity and highlight the therapeutic potential of targeting HIF in chemotherapy.

Abstract

Cisplatin is a highly effective, broad-spectrum chemotherapeutic drug, yet its clinical use and efficacy are limited by its side effects. Particularly, cancer patients receiving cisplatin chemotherapy have high incidence of kidney problems. Hypoxia-inducible factor (HIF) is the “master” transcription factor that is induced under hypoxia to trans-activate various genes for adaptation to the low oxygen condition. Numerous studies have reported that HIF activation protects against AKI and promotes kidney recovery in experimental models of cisplatin-induced acute kidney injury (AKI). In contrast, little is known about the effects of HIF on chronic kidney problems following cisplatin chemotherapy. Prolyl hydroxylase (PHD) inhibitors are potent HIF inducers that recently entered clinical use. By inducing HIF, PHD inhibitors may protect kidneys during cisplatin chemotherapy. However, HIF activation by PHD inhibitors may reduce the anti-cancer effect of cisplatin in tumors. Future studies should test PHD inhibitors in tumor-bearing animal models to verify their effects in kidneys and tumors.

A new insight into the treatment of renal anemia with HIF stabilizer

The long-term clinical experiences with recombinant human erythropoietin (rHuEPO) and its analog derivatives have clearly proven that correction of anemia with erythropoiesis stimulating agent (ESA) not only reduces blood transfusion and improves patients’ QOL but has multiple benefits for the concurrent complications of CKD such as Cardio-Renal–Anemia (CRA) syndrome and/or malnutrition-inflammation-atherosclerosis (MIA) syndrome.

Unlike ESA, the newly available agent, hypoxia-inducible factor (HIF) stabilizer, stimulates endogenous erythropoietin (EPO) by mimicking hypoxia with HIF prolyl hydroxylase domain enzyme (HIF-PHD) inhibition. The phase 2 and 3 clinical studies have shown that HIF stabilizers are as efficacious as ESA in ameliorating renal anemia. Whether the same clinical benefits on CRA and MIA syndrome hold true in patients given HIF stabilizers is a matter for future debate. Given that HIF stabilizers act on the multiple target genes, the use of this novel agent may lead to unwanted adverse events.

Launching HIF stabilizers into the treatment of renal anemia provokes a concern about how this alternative treatment will be taken up in the daily clinical practice. However, guideline-oriented strategies on how to use HIF stabilizer is not available at this limited point due to scant clinical information. Nevertheless, this opinion-based review provides a future insight into the management of renal anemia with HIF stabilizer by reference to the past experiences with ESA. HIF stabilizers can preferably be indicated for CRA syndrome at pre-dialysis stage, ESA resistant anemia at advanced CKD stage, and perhaps for dysregulated iron metabolism akin to MIA syndrome in patients on dialysis.

Contribution of hypoxia inducible factor-1 during viral infections

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that plays critical roles during the cellular response to hypoxia. Under normoxic conditions, its function is tightly regulated by the degradation of its alpha subunit (HIF-1α), which impairs the formation of an active heterodimer in the nucleus that otherwise regulates the expression of numerous genes. Importantly, HIF-1 participates in both cancer and infectious diseases unveiling new therapeutic targets for those ailments. Here, we discuss aspects related to the activation of HIF-1, the effects of this transcription factor over immune system components, as well as the involvement of HIF-1 activity in response to viral infections in humans. Although HIF-1 is currently being assessed in numerous clinical settings as a potential therapy for different diseases, up to date, there are no clinical studies evaluating the pharmacological modulation of this transcription factor as a possible new antiviral treatment. However, based on the available evidence, clinical trials targeting this molecule are likely to occur soon. In this review we discuss the role of HIF-1 in viral immunity, the modulation of HIF-1 by different types of viruses, as well as the effects of HIF-1 over their life cycle and the potential use of HIF-1 as a new target for the treatment of viral infections.

Endothelial prolyl hydroxylase 2 is necessary for angiotensin II-mediated renal fibrosis and injury

Angiotensin II (ANG II) is the key contributor to renal fibrosis and injury. The present study investigated the role of endothelium prolyl hydroxylase 2 (PHD2) in ANG II-mediated renal fibrosis and injury. In vitro, endothelial cells (ECs) were isolated from PHD2^f/f control [wild-type (WT)] mice or PHD2 EC knockout (PHD2^ECKO) mice. In vivo, WT and PHD2^ECKO mice were infused with ANG II (1,000 ng·kg^-1·min^-1) for 28 days. Renal fibrosis, reactive oxygen species (ROS), and iron contents were measured. Knockout of PHD2 resulted in a significant increase in the expression of hypoxia-inducible factor (HIF)-1α and HIF-2α in ECs. Intriguingly, knockout of PHD2 significantly reduced expression of the ANG II type 1 receptor (AT₁R) in ECs. WT mice infused with ANG II caused increases in renal fibrosis, ROS formation, and iron contents. ANG II treatment led to a downregulation of PHD1 expression and upregulation of HIF-1α and HIF-2α in the renal cortex and medulla. Knockout of PHD2 in EC blunted ANG II-induced downregulation of PHD1 expression. Furthermore, knockout of PHD2 in ECs attenuated ANG II-induced expression of HIF-1α, HIF-2α, transforming growth factor-β1, p47^phox, gp91^phox, heme oxygenase-1, and ferroportin. This was accompanied by a significant suppression of renal fibrosis, ROS formation, and iron accumulation. In summary, knockout of endothelial PHD2 suppressed the expression of AT₁R in ECs and blunted ANG II-induced downregulation of PHD1 and upregulation of HIF-α in the kidney. Our study, for the first time, demonstrates a necessary role of endothelial PHD2 in ANG II-mediated renal fibrosis and injury.

Atherosclerosis prediction by microarray-based DNA methylation analysis

Using a series of DNA methylation analysis, pathogenesis was investigated to identify the specific DNA methylation markers for diagnosing atherosclerosis. Firstly, with the chip platform of Illumina Human Methylation 450 BeadChip, a total of 1,458 CpGs, covering 971 differential methylated genes were extracted with stringent filtering criteria. Secondly, hierarchical clustering as a heat map was used to check on the dependability of differential methylated genes. Thirdly, the related GO terms and pathways were enriched by up- and down-methylated genes, respectively, after verifying the capacity of these differential methylated genes to distinguish between atherosclerosis and healthy controls. In total, 971 differential DNA methylated genes were identified (1,458 CpGs). Several important function regions were also identified, including cell adhesion, PI3K-Akt signaling pathway and transcription from RNA polymerase II promoter. This study indicates that patients with atherosclerosis have high levels of DNA methylation, which is promising for early diagnosis and treatment of atherosclerosis.

Physical health-related quality of life at higher achieved hemoglobin levels among chronic kidney disease patients: a systematic review and meta-analysis

BACKGROUND

The impact of anemia treatment with erythropoietin stimulating agents (ESA) on health-related quality of life (HRQOL) in chronic kidney disease (CKD) patients is controversial, particularly regarding optimal hemoglobin (Hb) target ranges.

METHODS

We conducted a systematic review and meta-analysis of observational studies and randomized controlled trials (RCT) with ESA to estimate the effect of different achieved Hb values on physical HRQOL and functionality. We searched PubMed, EMBASE, CENTRAL, PEDro, PsycINFO and Web of Science databases, until May 2020. Two authors independently extracted data from studies. We included observational and RCTs that enrolled CKD patients undergoing anemia treatment with ESA with different achieved Hb levels among groups. We excluded studies with achieved Hb < 9 g/dL. For the meta-analysis, we included RCTs with control groups achieving Hb 10-11.5 g/dL and active groups with Hb > 11.5 g/dL. We analyzed the standardized mean difference (SMD) between groups for physical HRQOL.

RESULTS

Among 8496 studies, fifteen RCTs and five observational studies were included for the systematic review. We performed the meta-analysis in a subset of eleven eligible RCTs. For physical role and physical function, SMDs were 0.0875 [95% CI: - 0.0025 - 0.178] and 0.08 [95% CI: - 0.03 - 0.19], respectively. For fatigue, SMD was 0.16 [95% CI: 0.09-0.24]. Subgroup analysis showed that trials with greater achieved Hb had greater pooled effects sizes - 0.21 [95% CI: 0.07-0.36] for Hb > 13 g/dL vs. 0.09 [95% CI: 0.02-0.16] for Hb 11.5-13 g/dL. Proportion of older and long-term diabetic patients across studies were associated with lower effect sizes.

CONCLUSION

Achieved hemoglobin higher than currently recommended targets may be associated with small but potentially clinically significant improvement in fatigue, but not in physical role or physical function. Younger and non-diabetic patients may experience more pronounced benefits of higher Hb levels after treatment with ESAs.

Oxygen homeostasis and cardiovascular disease: A role for HIF?

Hypoxia, the decline of tissue oxygen stress, plays a role in mediating cellular processes. Cardiovascular disease, relatively widespread with increased mortality, is closely correlated with oxygen homeostasis regulation. Besides, hypoxia-inducible factor-1(HIF-1) is reported to be a crucial component in regulating systemic hypoxia-induced physiological and pathological modifications like oxidative stress, damage, angiogenesis, vascular remodeling, inflammatory reaction, and metabolic remodeling. In addition, HIF1 controls the movement, proliferation, apoptosis, differentiation and activity of numerous core cells, such as cardiomyocytes, endothelial cells (ECs), smooth muscle cells (SMCs), and macrophages. Here we review the molecular regulation of HIF-1 in cardiovascular diseases, intended to improve therapeutic approaches for clinical diagnoses. Better knowledge of the oxygen balance control and the signal mechanisms involved is important to advance the development of hypoxia-related diseases.

Are prolyl-hydroxylase inhibitors potential alternative treatments for anaemia in patients with chronic kidney disease?

Prolyl-hydroxylase (PHD) inhibitors (PHD-I) are the most appealing drugs undergoing clinical development for the treatment of anaemia in patients with chronic kidney disease. PHD inhibition mimics the exposure of the body to hypoxia and activates the hypoxia-inducible factor system. Among many other pathways, this activation promotes the production of endogenous erythropoietin (EPO) and the absorption and mobilization of iron. PHD-I are given orally and, differing from erythropoiesis-stimulating agents (ESAs), they correct and maintain haemoglobin levels by stimulating endogenous EPO production. Their efficacy and safety are supported by several Phases I and II studies with relatively short follow-up. This class of drugs has the potential to have a better safety profile than ESAs and there may be additional advantages for cardiovascular disease (CVD), osteoporosis and metabolism. However, possible adverse outcomes are feared. These span from the worsening or occurrence of new cancer, to eye complications or pulmonary hypertension. The data from the ongoing Phase III studies are awaited to better clarify the long-term safety and possible advantages of PHD-I.

Klotho alleviates indoxyl sulfate-induced heart failure and kidney damage by promoting M2 macrophage polarization

Indoxyl sulfate (IS) is a protein-bound uremic toxin that can accumulate in patients with chronic kidney disease (CKD) or acute kidney injury (AKI) and cause kidney and cardiac dysfunction. Klotho is an anti-aging protein that has reno- and cardio-protective effects. We investigated whether Klotho could alleviate IS-induced heart failure and kidney damage by regulating macrophages, which play a key role in the inflammatory response in CKD and AKI. Treatment of THP-1-derived macrophages with IS induced the production of the pro-inflammatory cytokines TNFα, IL-6, and IL-1β, and stimulated M1 polarization. Additionally, IS induced downregulation of Klotho expression in macrophages. Overexpression of Klotho suppressed the IS-induced inflammatory response in macrophages by stimulating M2 polarization. It also alleviated IS-induced cardiac hypertrophy and renal fibrosis in mice. A reduction in IS-induced phosphorylation of NF-kB p65 was observed in response to Klotho overexpression, suggesting that Klotho alleviates kidney and cardiac injury by inactivating NF-kB signaling and promoting macrophage M2 polarization.

Hypoxia-Inducible Factor-1α: The Master Regulator of Endothelial Cell Senescence in Vascular Aging

Aging is one of the hottest topics in biomedical research. Advances in research and medicine have helped to preserve human health, leading to an extension of life expectancy. However, the extension of life is an irreversible process that is accompanied by the development of aging-related conditions such as weakness, slower metabolism, and stiffness of vessels. It also debated that aging can be considered an actual disease with aging-derived comorbidities, including cancer or cardiovascular disease. Currently, cardiovascular disorders, including atherosclerosis, are considered as premature aging and represent the first causes of death in developed countries, accounting for 31% of annual deaths globally. Emerging evidence has identified hypoxia-inducible factor-1α as a critical transcription factor with an essential role in aging-related pathology, in particular, regulating cellular senescence associated with cardiovascular aging. In this review, we will focus on the regulation of senescence mediated by hypoxia-inducible factor-1α in age-related pathologies, with particular emphasis on the crosstalk between endothelial and vascular cells in age-associated atherosclerotic lesions. More specifically, we will focus on the characteristics and mechanisms by which cells within the vascular wall, including endothelial and vascular cells, achieve a senescent phenotype.

A network pharmacology approach to discover action mechanisms of Yangxinshi Tablet for improving energy metabolism in chronic ischemic heart failure

ETHNOPHARMACOLOGICAL RELEVANCE

Most cardiovascular diseases ultimately result in heart failure, an intractable problem in modern medicine. Yangxinshi tablet (YXS) is a Chinese medicine formula that is used clinically to treat coronary heart disease. However, the active compounds, potential targets, and pharmacological and molecular mechanism of its anti-heart failure activity remain unclear. Therefore, further investigation is required.

AIM OF STUDY

Active ingredients and potential targets of YXS for treating heart failure have been reported previously. However, the molecular functions or biological processes of YXS in energy metabolism have not been discovered. To date, no experimental study to validate the potential anti-heart failure mechanism of YXS. The aim of this study was to study the therapeutic effect of YXS on rats with chronic ischemic heart failure by evaluating rat cardiac function and exercise tolerance, and to explore its potential mechanism by network pharmacology, western blotting, quantitative RT-PCR and histological analysis.

MATERIALS AND METHODS

In this investigation, chronic ischemic heart failure rats were randomly assigned to five groups: control group (sham operation), model group (0.5% CMC-Na), trimetazidine group (positive control) and two YXS groups (low- and high-dose groups). Experimental rats were treated by gavage with 10 mg/kg/d (clinical equivalent dose) trimetazidine (TMZ), 500 mg/kg/d (clinical equivalent dose) YXS and 1000 mg/kg/d YXS, respectively, for 5 weeks. The cardiac functions of rats were detected by High-Resolution In Vivo Imaging System. We elucidated novel understanding of the active compounds of YXS in rat plasma and predicted the energy metabolism related targets and processes for heart failure. Then, we validated experimentally the targets and mechanism of YXS on these pathological processes in vivo.

RESULTS

It was found that YXS was able to effectively improve cardiac LVIDs, LVEDV, LVESV and EF, decrease myocardial oxygen consumption and reduce myocardial infarct size in rats with chronic ischemic heart failure was similar to that of TMZ. We identified 63 major candidate targets for YXS that are closely to heart failure progression. Enrichment analysis revealed key targets for YXS associated to oxygen delivery, glucose utilization, and mitochondrial biogenesis. Meanwhile, we validated that YXS could promote the expression of downstream HIF-1α, PGC1α and GLUT4 by increasing phosphorylation of PI3K, Akt, mTOR, rpS6 and AMPK. The results show that YXS could activate related PI3K/Akt/mTOR/rpS6/HIF-1α and AMPK/PGC1α/GLUT4 signaling pathways in chronic ischemic heart failure rats. Further experiments demonstrated that YXS increased mitochondrial biogenesis in chronic ischemic heart failure rats and improved exercise tolerance CONCLUSION: YXS treated chronic ischemic heart failure through activating its targets which play pivotal roles in oxygen delivery, glucose utilization and mitochondrial biogenesis to improve energy metabolism through a multi-component, multi-level, multi-target, multi-pathway and multi-mechanism approaches.

Effects of a prolyl hydroxylase inhibitor on kidney and cardiovascular complications in a rat model of chronic kidney disease

Cardiovascular disease (CVD) is the main cause of death in patients with kidney disease. Hypoxia plays a crucial role in the progression of chronic kidney disease (CKD) and cardiovascular disease, which is associated with fibrosis, inflammation, and oxidative injury. Previous studies have indicated that prolyl hydroxylase (PHD) inhibitors, stabilizers of hypoxia-inducible factors (HIFs), can be used to treat acute organ injuries such as renal ischemia-reperfusion, myocardial infarction, and, in some contexts, CKD. However, the effects of PHD inhibitors on cardiovascular complications in CKD remain unknown. In the present study, we investigated whether HIF activation has a beneficial effect on kidney and cardiovascular outcomes in the remnant kidney model. We used the 5/6 nephrectomy model with the nitric oxide synthase inhibitor N^ω-nitro-l-arginine (20 mg/L in the drinking water). Rats received diet with 0.005% enarodustat (PHD inhibitor) or vehicle for 8 wk starting 2 wk before 5/6 nephrectomy. Activation of HIF by the PHD inhibitor reduced cardiac hypertrophy and ameliorated myocardial fibrosis in association with restored capillary density and improvement in mitochondrial morphology. With regard to kidneys, enarodustat ameliorated fibrosis in association with reduced proinflammatory cytokine expression, reduced apoptosis, and restored capillary density, even though renal endpoints such as proteinuria and serum creatinine levels were not significantly affected by enarodustat, except for blood urea nitrogen levels at 4 wk. In addition, cardiac hypertrophy marker genes, including atrial natriuretic peptide, were suppressed in P19CL6 cells treated with enarodustat. These findings suggest that PHD inhibitors might show beneficial effects in cardiovascular complications caused by CKD.

Intrabody against prolyl hydroxylase 2 promotes angiogenesis by stabilizing hypoxia-inducible factor-1α

Hypoxia-inducible factor (HIF)-1α is a crucial transcription factor that regulates the expression of target genes involved in angiogenesis. Prolyl hydroxylase 2 (PHD2) dominantly hydroxylates two highly conserved proline residues of HIF-1α to promote its degradation. This study was designed to construct an intrabody against PHD2 that can inhibit PHD2 activity and promote angiogenesis. Single-chain variable fragment (scFv) against PHD2, INP, was isolated by phage display technique and was modified with an endoplasmic reticulum (ER) sequence to obtain ER-retained intrabody against PHD2 (ER-INP). ER-INP was efficiently expressed and bound to PHD2 in cells, significantly increased the levels of HIF-1α, and decreased hydroxylated HIF-1α in human embryonic kidney cell line (HEK293) cells and mouse mononuclear macrophage leukaemia cell line (RAW264.7) cells. ER-INP has shown distinct angiogenic activity both in vitro and in vivo, as ER-INP expression significantly promoted the migration and tube formation of human umbilical vein endothelial cells (HUVECs) and enhanced angiogenesis of chick chorioallantoic membranes (CAMs). Furthermore, ER-INP promoted distinct expression and secretion of a range of angiogenic factors. To the best of our knowledge, this is the first study to report an ER-INP intrabody enhancing angiogenesis by blocking PHD2 activity to increase HIF-1α abundance and activity. These results indicate that ER-INP may play a role in the clinical treatment of tissue injury and ischemic diseases in the future.

The potential role of vascular alterations and subsequent impaired liver blood flow and hepatic hypoxia in the pathophysiology of non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) covers a spectrum of disease ranging from steatosis to steatohepatitis (NASH) and fibrosis, but the underlying pathophysiological mechanisms remain largely unknown. As there is currently no approved pharmacological therapy and the prevalence of NAFLD keeps increasing, understanding of its pathophysiology is crucial. We hypothesise that vascular alterations in early NAFLD play a role in the progression of the disease by inducing an increased intrahepatic vascular resistance and consequently relative hypoxia in the liver. Evidence of the detrimental effects of hypoxia in NAFLD has already been observed in liver surgery, where the outcomes of steatotic livers after ischaemia-reperfusion are worse than in healthy livers, and in obstructive sleep apnoea, which is an independent risk factor of NAFLD. Moreover, early histological damage in NAFLD is situated in the pericentral zone, which is also the first zone to be affected by a decreased oxygen tension because of the unique hepatic vacsular anatomy that causes the pericentral oxygen tension to be the lowest. Angiogenesis is also a characteristic of NAFLD, driven by hypoxia-induced mechanisms, as demonstrated in both animal models and in humans with NAFLD. Relative hypoxia is most probably induced by impaired blood flow to the liver, caused by increased intrahepatic vascular resistance. An increased intrahepatic vascular resistance early in the development of disease has been convincingly demonstrated in several animal models of NAFLD, whereas an increased portal pressure, a consequence of increased intrahepatic vascular resistance, has been proven in patients with NAFLD. Animal studies demonstrated a decreased intrahepatic effect of vasodilators and an increased reactivity to vasoconstrictors that results in an increased intrahepatic vascular resistance, thus the presence of a functional component. Pharmacological products that target vasoregulation can hence improve the intrahepatic vascular resistance and this might prevent or reverse progression of NAFLD, representing an important therapeutic option to study. Some of the drugs currently under evaluation in clinical trials for NASH have interesting properties related to the hepatic vasculature. Some other interesting drugs have been tested in animal models but further study in patients with NAFLD is warranted. In summary, in this paper we summarise the evidence that leads to the hypothesis that an increased intrahepatic vascular resistance and subsequent parenchymal hypoxia in early NAFLD is an important pathophysiological driving mechanism for the progression of the disease.

Anemia of inflammation

Anemia of inflammation (AI), also known as anemia of chronic disease (ACD), is regarded as the most frequent anemia in hospitalized and chronically ill patients. It is prevalent in patients with diseases that cause prolonged immune activation, including infection, autoimmune diseases, and cancer. More recently, the list has grown to include chronic kidney disease, congestive heart failure, chronic pulmonary diseases, and obesity. Inflammation-inducible cytokines and the master regulator of iron homeostasis, hepcidin, block intestinal iron absorption and cause iron retention in reticuloendothelial cells, resulting in iron-restricted erythropoiesis. In addition, shortened erythrocyte half-life, suppressed erythropoietin response to anemia, and inhibition of erythroid cell differentiation by inflammatory mediators further contribute to AI in a disease-specific pattern. Although the diagnosis of AI is a diagnosis of exclusion and is supported by characteristic alterations in iron homeostasis, hypoferremia, and hyperferritinemia, the diagnosis of AI patients with coexisting iron deficiency is more difficult. In addition to treatment of the disease underlying AI, the combination of iron therapy and erythropoiesis-stimulating agents can improve anemia in many patients. In the future, emerging therapeutics that antagonize hepcidin function and redistribute endogenous iron for erythropoiesis may offer additional options. However, based on experience with anemia treatment in chronic kidney disease, critical illness, and cancer, finding the appropriate indications for the specific treatment of AI will require improved understanding and a balanced consideration of the contribution of anemia to each patient's morbidity and the impact of anemia treatment on the patient's prognosis in a variety of disease settings.