Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitors and Iron Metabolism

HIF-PH inhibitors induce pseudohypoxia in T cells and suppress the growth of microsatellite stable colorectal cancer by enhancing antitumor immune responses

BACKGROUND

Recent studies have revealed that CD8+ T cells can be activated via genetic upregulation of HIF-1α, thereby augmenting antitumor effector functions. HIF-1α upregulation can be attained by inhibiting HIF-prolyl hydroxylase (HIF-PH) under normoxic conditions, termed pseudohypoxia. This study investigated whether pseudohypoxia induced by HIF-PH inhibitors suppresses Microsatellite stable (MSS) colorectal cancer (CRC) by affecting tumor immune response.

METHODS

The HIF-PH inhibitors Roxadustat and Vadadustat were utilized in this study. In vitro, we assessed the effects of HIF-PH inhibitors on human and murine colon cancer cell lines (SW480, HT29, Colon26) and murine T cells. In vivo experiments were performed with mice bearing Colon26 tumors to evaluate the effect of these inhibitors on tumor immune responses. Tumor and spleen samples were analyzed using immunohistochemistry, RT-qPCR, and flow cytometry to elucidate potential mechanisms.

RESULTS

HIF-PH inhibitors demonstrated antitumor effects in vivo but not in vitro. These inhibitors enhanced the tumor immune response by increasing the infiltration of CD8+ and CD4+ tumor-infiltrating lymphocytes (TILs). HIF-PH inhibitors induced IL-2 production in splenic and intratumoral CD4+ T cells, promoting T cell proliferation, differentiation, and immune responses. Roxadustat synergistically enhanced the efficacy of anti-PD-1 antibody for MSS cancer by increasing the recruitment of TILs and augmenting effector-like CD8+ T cells.

CONCLUSION

Pseudohypoxia induced by HIF-PH inhibitors activates antitumor immune responses, at least in part, through the induction of IL-2 secretion from CD4+ T cells in the spleen and tumor microenvironment, thereby enhancing immune efficacy against MSS CRC.

Elucidating the Role of HIF-1α/YAP Signaling Pathway in Regulating Inflammation in Human Periodontal Stem Cells: An in vitro Study

Background and Objective

Periodontitis is a chronic inflammatory disease caused by dental plaque accumulation, leading to damage of periodontal tissues and potential tooth loss. Understanding the mechanisms of periodontitis, particularly the role of hypoxia in inflammation, is critical for identifying novel therapeutic strategies. This study investigated the effects of the prolyl hydroxylase (PHD) inhibitor DMOG on pro-inflammatory cytokine expression in human periodontal ligament stem cells (hPDLSCs) and examined the involvement of the HIF-1α/YAP signaling path ay in modulating inflammation.

Materials and Methods

hPDLSCs were cultured and treated with lipopolysaccharide (LPS) to induce inflammation, followed by DMOG treatment. Cell proliferation was assessed using the CCK-8 assay, while ELISA and RT-qPCR evaluated the expression levels of HIF-1α, IL-1β, TNF-α, and YAP. YAP expression was knocked down using siRNA transfection to examine its effects on inflammatory cytokines.

Results

DMOG significantly increased HIF-1α expression while reducing IL-1β and TNF-α levels in LPS-treated hPDLSCs. 0.1 mmol/L DMOG inhibited cell proliferation after 72 hours (P < 0.001). ELISA results showed that HIF-1α concentrations in the LPS + DMOG group were significantly higher than in the LPS group (P < 0.01), while IL-1β and TNF-α levels were significantly reduced (P < 0.01). RT-qPCR confirmed these trends, showing reduced mRNA levels of IL-1β and TNF-α and increased YAP expression in the LPS + DMOG group (P < 0.0001). YAP knockdown via siRNA transfection reversed these effects, increasing IL-1β and TNF-α levels (P < 0.01) while significantly reducing HIF-1α expression (P < 0.05).

Conclusion

This study demonstrated that DMOG reduces inflammatory cytokine expression in hPDLSCs by stabilizing HIF-1α and activating the YAP signaling pathway. These findings provide a mechanistic basis for targeting the HIF-1α/YAP axis to control periodontal inflammation and support the potential of PHD inhibitors as therapeutic agents for periodontitis.

Hypoxia-induced conversion of sensory Schwann cells into repair cells is regulated by HDAC8

After a peripheral nerve injury, Schwann cells (SCs), the myelinating glia of the peripheral nervous system, convert into repair cells that foster axonal regrowth, and then remyelinate or re-ensheath regenerated axons, thereby ensuring functional recovery. The efficiency of this mechanism depends however on the time needed for axons to regrow. Here, we show that ablation of histone deacetylase 8 (HDAC8) in SCs accelerates the regrowth of sensory axons and sensory function recovery. We found that HDAC8 is specifically expressed in sensory SCs and regulates the E3 ubiquitin ligase TRAF7, which destabilizes hypoxia-inducible factor 1-alpha (HIF1α) and counteracts the phosphorylation and upregulation of c-Jun, a major inducer of the repair SC phenotype. Our study indicates that this phenotype switch is regulated by different mechanisms in sensory and motor SCs and is accelerated by HDAC8 downregulation, which promotes sensory axon regeneration and sensory function recovery.

Influencing factors of clinical efficacy of roxadustat among hemodialysis patients

OBJECTIVE

To explore independent influencing factors for clinical efficacy of roxadustat in hemodialysis patients.

METHODS

Hemodialysis patients treated with roxadustat were enrolled. The plasma trough concentrations of roxadustat were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A multiple logistic regression model was established to determine the factors that affect clinical efficacy of roxadustat in patients undergoing hemodialysis.

RESULTS

A total of 67 hemodialysis patients were enrolled in the study. The results showed that age, blood trough concentration of roxadustat, and baseline hemoglobin (Hb) level were independent factors of clinical efficacy of roxadustat (OR = 1.06, p = .025 for age; OR = 1.001, p = .037 for plasma concentration; and OR = 0.941, p = .003 for baseline Hb), with an AUC score of 0.859.

CONCLUSIONS

Age, blood trough concentration of roxadustat, and baseline Hb level were independent influencing factors of the response to roxadustat in hemodialysis patients.

The Efficacy and Safety of Roxadustat for Anemia in Hemodialysis Patients with Chronic Kidney Disease: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Patients undergoing hemodialysis (HD) for chronic kidney disease (CKD) often encounter anemia. Roxadustat has not only undergone phase II-III clinical trials in patients suffering from CKD and undergoing HD; a number of post-marketing clinical studies have been conducted using the drug. This article was to assess the effectiveness and safety of roxadustat in managing anemia among patients with CKD undergoing HD.

METHODS

A thorough search was performed across eight databases, including PubMed, Web of Science, Cochrane Library, Embase, Wan Fang, China National Knowledge Infrastructure (CNKI), Chongqing VIP (CQ VIP), and SinoMed to identify randomized clinical trials (RCTs) examining the effectiveness and safety of roxadustat in managing anemia among individuals suffering from CKD and undergoing HD. This search included studies from the inception of these databases to April 2023.

RESULTS

Two phase II, one phase III, and 16 post-marketing studies with 1688 participants were included. Serum iron (SI), transferrin, and total iron-binding capacity (TIBC) levels changed from baseline (∆SI, ∆transferrin, and ∆TIBC) and were significantly more increased for roxadustat than for erythropoiesis-stimulating agents (ESAs): MD 2.55, (95% CI 1.51 to 3.60), p < 0.00001; MD 0.55, (95% CI 0.41 to 0.69), p < 0.00001; and MD 6.54, (95% CI 4.50 to 8.59), p < 0.00001, respectively. Roxadustat was not inferior to ESAs with regard to increasing Hb (∆Hb) levels [MD 1.17 (95% CI 0.71 to 1.63), p < 0.00001] (g/dL). No statistically significant distinctions of the ∆ferritin, ∆hepcidin, and transferrin saturation (TSAT) from baseline (∆TSAT) level were identified between roxadustat and ESAs. C-reactive protein (CRP) levels changed from baseline (∆CRP) and were significantly more reduced for roxadustat than for ESAs. As for safety, the analysis indicated no notable difference in the occurrence of adverse events (AEs) and serious adverse events (SAEs) between roxadustat and ESAs.

CONCLUSIONS

This meta-analysis demonstrated that roxadustat outperformed ESAs in enhancing SI, transferrin, and TIBC levels while also decreasing CRP levels. Roxadustat was not inferior to ESAs in terms of improving Hb levels and safety. These findings suggest that roxadustat was well tolerated and a potent alternative to ESAs in managing anemia among patients suffering from CKD and undergoing HD.

Erythrocyte indices and response to hypoxia-inducible factor prolyl hydroxylase inhibitors in chronic kidney disease patients with renal anemia: a retrospective study

BACKGROUND

Although erythropoiesis-stimulating agents (ESAs) have been the standard treatment for renal anemia, ESA hyporesponsiveness remains a concern. Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are a new class of agents indicated for renal anemia. Several lines of evidence indicate that HIF-PHIs affect erythrocyte indices; nonetheless, their clinical significance remains unclear.

METHODS

We retrospectively analyzed data from 233 non-dialysis-dependent chronic kidney disease patients who initiated either ESA (darbepoetin) or HIF-PHI for the treatment of anemia. We analyzed the changes in hemoglobin levels three months after the initiation of anti-anemic treatments, examining their association with changes in erythrocyte indices.

RESULTS

Both ESA and HIF-PHIs significantly increased hemoglobin levels after three months of treatment. In the HIF-PHI group, the increase in hemoglobin levels was positively correlated with the increase in mean corpuscular volume (MCV) levels, a finding that was not observed in the ESA group. In a subgroup analysis based on the mean reference range value for MCV (90.9 fL), a significant difference in the proportion of patients with improved anemia was observed between ESA and HIF-PHIs in patients with lower MCV values. Logistic regression and interaction analyses confirmed that there was a significant interaction between baseline MCV values and the effectiveness of anti-anemic drugs, independently of other covariates.

CONCLUSIONS

An increase in hemoglobin levels is associated with an increase in MCV in patients treated with HIF-PHIs. The anti-anemic effects of ESA and HIF-PHIs may be influenced by baseline MCV values. However, long-term consequences need further evaluation.

Iron chelators as mitophagy agents: Potential and limitations

Mitochondrial autophagy (mitophagy) is very important process for the maintenance of cellular homeostasis, functionality and survival. Its dysregulation is associated with high risk and progression numerous serious diseases (e.g., oncological, neurodegenerative and cardiovascular ones). Therefore, targeting mitophagy mechanisms is very hot topic in the biological and medicinal research. The interrelationships between the regulation of mitophagy and iron homeostasis are now becoming apparent. In short, mitochondria are central point for the regulation of iron homeostasis, but change in intracellular cheatable iron level can induce/repress mitophagy. In this review, relationships between iron homeostasis and mitophagy are thoroughly discussed and described. Also, therapeutic applicability of mitophagy chelators in the context of individual diseases is comprehensively and critically evaluated.

Hypoxia Pathways in Parkinson's Disease: From Pathogenesis to Therapeutic Targets

The human brain is highly dependent on oxygen, utilizing approximately 20% of the body's oxygen at rest. Oxygen deprivation to the brain can lead to loss of consciousness within seconds and death within minutes. Recent studies have identified regions of the brain with spontaneous episodic hypoxia, referred to as "hypoxic pockets". Hypoxia can also result from impaired blood flow due to conditions such as heart disease, blood clots, stroke, or hemorrhage, as well as from reduced oxygen intake or excessive oxygen consumption caused by factors like low ambient oxygen, pulmonary diseases, infections, inflammation, and cancer. Severe hypoxia in the brain can manifest symptoms similar to Parkinson's disease (PD), including cerebral edema, mood disturbances, and cognitive impairments. Additionally, the development of PD appears to be closely associated with hypoxia and hypoxic pathways. This review seeks to investigate the molecular interactions between hypoxia and PD, emphasizing the pathological role of hypoxic pathways in PD and exploring their potential as therapeutic targets.

Association between roxadustat use and suppression of thyroid function: a systematic review and meta-analysis

BACKGROUND

Based on several case reports and observational studies, there is a growing concern regarding the potential association between roxadustat, a hypoxia-inducible factor prolyl-hydroxylase inhibitor, and suppression of thyroid function. In this systematic review and meta-analysis (PROSPERO: CRD42023471516), we aimed to evaluate the relationship between roxadustat use and suppression of thyroid function.

METHODS

We conducted a comprehensive search of MEDLINE via PubMed, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials databases using the search term "roxadustat" to identify all relevant studies. The study population comprised adults with renal anemia who participated in a randomized controlled trial or observational study, with roxadustat as the intervention and a placebo or erythropoiesis-stimulating agent (ESA) as the comparator. The primary outcome was suppression of thyroid function and the secondary outcome was hypothyroidism. A meta-analysis was conducted using the DerSimonian-Laird random effects model based on the size of the intention-to-treat population, and the odds ratio (OR) and 95% confidence interval (CI) were calculated. Two reviewers independently screened the articles, extracted data, and assessed studies using the ROBINS-I tool.

RESULTS

Of the six studies eligible for inclusion, a meta-analysis was performed using data from two observational studies comparing roxadustat and ESA. The meta-analysis showed that the incidence of suppression of thyroid function was significantly higher with roxadustat use than with ESA use (OR: 6.45; 95% CI: 3.39-12.27; I2 = 12%). Compared with ESA, roxadustat seemed to potentially increase the risk for suppression of thyroid function in patients with renal anemia.

CONCLUSIONS

Our findings highlighted the importance of monitoring thyroid function in patients treated with roxadustat. The results of this review may enhance the safety of using roxadustat to treat renal anemia through advance recognition of the risk for suppression of thyroid function.

Anemia of Chronic Kidney Disease-A Narrative Review of Its Pathophysiology, Diagnosis, and Management

Anemia is one of the most common chronic kidney disease (CKD) complications. It negatively affects patients' quality of life and clinical outcomes. The pathophysiology of anemia in CKD involves the interplay of various factors such as erythropoietin (EPO) deficiency, iron dysregulation, chronic inflammation, bone marrow dysfunction, and nutritional deficiencies. Despite recent advances in understanding this condition, anemia still remains a serious clinical challenge in population of patients with CKD. Several guidelines have been published with the aim to systematize the diagnostic approach and treatment of anemia; however, due to emerging data, many recommendations vary between publications. Recent studies indicate a potential of novel biomarkers to evaluate anemia and related conditions such as iron deficiency, which is often present in CKD patients. Our article aims to summarize the pathophysiology of anemia in CKD, as well as the diagnosis and management of this condition, including novel therapeutic approaches such as hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHI). Understanding these complex subjects is crucial for a targeted approach to diagnose and treat patients with anemia in CKD effectively.

Iron Absorption: Molecular and Pathophysiological Aspects

Iron is an essential nutrient for growth among all branches of life, but while iron is among the most common elements, bioavailable iron is a relatively scarce nutrient. Since iron is fundamental for several biological processes, iron deficiency can be deleterious. On the other hand, excess iron may lead to cell and tissue damage. Consequently, iron balance is strictly regulated. As iron excretion is not physiologically controlled, systemic iron homeostasis is maintained at the level of absorption, which is mainly influenced by the amount of iron stores and the level of erythropoietic activity, the major iron consumer. Here, we outline recent advances that increased our understanding of the molecular aspects of iron absorption. Moreover, we examine the impact of these recent insights on dietary strategies for maintaining iron balance.

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.

Minerals and the Menstrual Cycle: Impacts on Ovulation and Endometrial Health

The role of minerals in female fertility, particularly in relation to the menstrual cycle, presents a complex area of study that underscores the interplay between nutrition and reproductive health. This narrative review aims to elucidate the impacts of minerals on key aspects of the reproductive system: hormonal regulation, ovarian function and ovulation, endometrial health, and oxidative stress. Despite the attention given to specific micronutrients in relation to reproductive disorders, there is a noticeable absence of a comprehensive review focusing on the impact of minerals throughout the menstrual cycle on female fertility. This narrative review aims to address this gap by examining the influence of minerals on reproductive health. Each mineral's contribution is explored in detail to provide a clearer picture of its importance in supporting female fertility. This comprehensive analysis not only enhances our knowledge of reproductive health but also offers clinicians valuable insights into potential therapeutic strategies and the recommended intake of minerals to promote female reproductive well-being, considering the menstrual cycle. This review stands as the first to offer such a detailed examination of minerals in the context of the menstrual cycle, aiming to elevate the understanding of their critical role in female fertility and reproductive health.

Tubular Endogenous Erythropoietin Protects Renal Function against Ischemic Reperfusion Injury

Many large-scale studies show that exogenous erythropoietin, erythropoiesis-stimulating agents, lack any renoprotective effects. We investigated the effects of endogenous erythropoietin on renal function in kidney ischemic reperfusion injury (IRI) using the prolyl hydroxylase domain (PHD) inhibitor, Roxadustat (ROX). Four h of hypoxia (7% O2) and 4 h treatment by ROX prior to IRI did not improve renal function. In contrast, 24-72 h pretreatment by ROX significantly improved the decline of renal function caused by IRI. Hypoxia and 4 h ROX increased interstitial cells-derived Epo production by 75- and 6-fold, respectively, before IRI, and worked similarly to exogenous Epo. ROX treatment for 24-72 h increased Epo production during IRI by 9-fold. Immunohistochemistry revealed that 24 h ROX treatment induced Epo production in proximal and distal tubules and worked similarly to endogenous Epo. Our data show that tubular endogenous Epo production induced by 24-72 h ROX treatment results in renoprotection but peritubular exogenous Epo production by interstitial cells induced by hypoxia and 4 h ROX treatment did not. Stimulation of tubular, but not peritubular, Epo production may link to renoprotection.

Disproportionality Analysis on Hypothyroidism With Roxadustat Using the Japanese Adverse Drug Event Database

Hypoxia-inducible factor prolyl-hydroxylase inhibitor (HIF-PHI) is a novel agent for the treatment of renal anemia. HIF-PHI increases endogenous erythropoietin production by inhibiting the degradation of an erythropoietin transcription factor. Although beneficial effects are expected from HIF-PHI, its novel mechanism raises concerns regarding the risk of potential adverse events. The cases of hypothyroidism, which had not been reported in clinical trials, were reported after the administration of roxadustat in a real-world setting. However, the effects of HIF-PHIs on thyroid function have not yet been fully evaluated. This study aimed to assess the clinical impact of HIF-PHIs on thyroid function using the Japanese Adverse Drug Event Report database, a spontaneous reporting system in Japan, because HIF-PHIs were made available in Japan before they were available in other countries. Although a disproportionality signal for hypothyroidism was detected with roxadustat (reporting odds ratio [ROR]:22.1, 95% confidence interval [CI]:18.3-26.7, no signals were detected with another HIF-PHI, daprodustat (ROR:1.3, 95%CI:0.3-5.4), and epoetin beta pegol (ROR:1.2, 95%CI:0.5-2.7). Signals of hypothyroidism due to roxadustat were also detected regardless of age or sex. Approximately 50% of hypothyroidism cases were reported within 50 days of starting roxadustat use. These results indicate that roxadustat use may be related to the development of hypothyroidism. The need for monitoring of thyroid function should be alerted during roxadustat administration regardless of age or sex.

Hypoxia-Inducible Factor-Prolyl Hydroxylase Inhibitor Improves Leukocyte Energy Metabolism in Hereditary Hemorrhagic Telangiectasia

The interplay between hypoxia-inducible factors (HIFs) and transforming growth factor beta (TGF-β) is critical for both inflammation and angiogenesis. In hereditary hemorrhagic telangiectasia (HHT), we have previously observed that impairment of the TGF-β pathway is associated with downregulation of HIF-1α. HIF-1α accumulation is mandatory in situations of altered energy demand, such as during infection or hypoxia, by adjusting cell metabolism. Leukocytes undergo a HIF-1α-dependent switch from aerobic mitochondrial respiration to anaerobic glycolysis (glycolytic switch) after stimulation and during differentiation. We postulate that the decreased HIF-1α accumulation in HHT leads to a clinically observed immunodeficiency in these patients. Examination of HIF-1α and its target genes in freshly isolated peripheral blood mononuclear cells (PBMCs) from HHT patients revealed decreased gene expression and protein levels of HIF-1α and HIF-1α-regulated glycolytic enzymes. Treatment of these cells with the HIF-prolyl hydroxylase inhibitor, Roxadustat, rescued their ability to accumulate HIF-1α protein. Functional analysis of metabolic flux using a Seahorse FX extracellular flux analyzer showed that the extracellular acidification rate (indicator of glycolytic turnover) after Roxadustat treatment was comparable to non-HHT controls, while oxygen consumption (indicator of mitochondrial respiration) was slightly reduced. HIF stabilization may be a potential therapeutic target in HHT patients suffering from infections.

HIF2α, Hepcidin and their crosstalk as tumour-promoting signalling

Not all aspects of the disruption of iron homeostasis in cancer have been fully elucidated. Iron accumulation in cancer cells is frequent for many solid tumours, and this is often accompanied by the contemporary rise of two key iron regulators, HIF2α and Hepcidin. This scenario is different from what happens under physiological conditions, where Hepcidin parallels systemic iron concentrations while HIF2α levels are inversely associated to Hepcidin. The present review highlights the increasing body of evidence for the pro-tumoral effect of HIF2α and Hepcidin, discusses the possible imbalance in HIF2α, Hepcidin and iron homeostasis during cancer, and explores therapeutic options relying on these pathways as anticancer strategies.

Progress in the Detection of Erythropoietin in Blood, Urine, and Tissue

Detection of erythropoietin (Epo) was difficult until a method was developed by the World Anti-Doping Agency (WADA). WADA recommended the Western blot technique using isoelectric focusing (IEF)-PAGE to show that natural Epo and injected erythropoiesis-stimulating agents (ESAs) appear in different pH areas. Next, they used sodium N-lauroylsarcosinate (SAR)-PAGE for better differentiation of pegylated proteins, such as epoetin β pegol. Although WADA has recommended the use of pre-purification of samples, we developed a simple Western blotting method without pre-purification of samples. Instead of pre-purification, we used deglycosylation of samples before SDS-PAGE. The double detection of glycosylated and deglycosylated Epo bands increases the reliability of the detection of Epo protein. All of the endogenous Epo and exogenous ESAs shift to 22 kDa, except for Peg-bound epoetin β pegol. All endogenous Epo and exogenous ESAs were detected as 22 kDa deglycosylated Epo by liquid chromatography/mass spectrum (LC/MS) analysis. The most important factor for the detection of Epo is the selection of the antibody against Epo. WADA recommended clone AE7A5, and we used sc-9620. Both antibodies are useful for the detection of Epo protein by Western blotting.