Randomised clinical trial: a phase 1b study of GB004, an oral HIF-1α stabiliser, for treatment of ulcerative colitis

Clinical usefulness of hypoxia imaging colonoscopy for the objective measurement of ulcerative colitis disease activity

BACKGROUND AND AIMS

Colonic mucosal hypoxia is associated with mucosal inflammation in ulcerative colitis (UC). We aimed to assess the clinical usefulness of hypoxia imaging colonoscopy for the evaluation of clinical, endoscopic, and histologic disease activities of UC.

METHODS

This retrospective cohort study comprised 100 consecutive patients with UC who underwent hypoxia imaging colonoscopy between September 2022 and September 2023 at the University of Tsukuba Hospital. Colonic tissue oxygen saturation (StO2) was measured at the biopsy sites, and StO2 values between different disease activities were compared. Receiver-operating characteristic (ROC) analysis was used to calculate the area under the ROC curve (AUROC).

RESULTS

A significant correlation was identified between rectal StO2 and the Simple Clinical Colitis Activity Index, with moderate accuracy to predict bowel urgency at a 40.5% cutoff (AUROC, .74; 95% confidence interval [CI], .62-.87). Our analysis of 490 images showed median StO2 values for Mayo endoscopic subscores 0, 1, 2, and 3 as 52% (interquartile range [IQR], 48%-56%), 47% (IQR, 43%-52%), 42% (IQR, 38.8%-47%), and 39.5% (IQR, 37.3%-41.8%), respectively. Differences for all pairs were significant. Median StO2 was 49% (IQR, 44%-54%) for Geboes scores 0 to 2, significantly higher than histologically active disease (Geboes score ≥3). At a colonic StO2 cutoff of 45.5%, AUROCs for endoscopically and histologically active diseases were .79 (95% CI, .74-.84) and .72 (95% CI, .66-.77).

CONCLUSIONS

StO2 obtained by hypoxia imaging colonoscopy is useful for assessing clinical, endoscopic, and histologic activities of UC, suggesting that StO2 may be a novel and objective endoscopic measurement.

Cutting Edge: Hypoxia Sensing by the Histone Demethylase UTX (KDM6A) Limits Colitogenic CD4+ T Cells in Mucosal Inflammation

Hypoxia is a hallmark of inflammatory conditions (e.g., inflammatory bowel disease [IBD]), and adaptive responses have consequently evolved to protect against hypoxia-associated tissue injury. Because augmenting hypoxia-induced protective responses is a promising therapeutic approach for IBD, a more complete understanding of these pathways is needed. Recent work has demonstrated that the histone demethylase UTX is oxygen-sensitive, but its role in IBD is unclear. In this study, we show that hypoxia-induced deactivation of UTX downregulates T cell responses in mucosal inflammation. Hypoxia results in decreased T cell proinflammatory cytokine production and increased immunosuppressive regulatory T cells, and these findings are recapitulated by UTX deficiency. Hypoxia leads to T cell accumulation of H3K27me3 histone modifications, suggesting that hypoxia impairs UTX's histone demethylase activity to dampen T cell colitogenic activity. Finally, T cell-specific UTX deletion ameliorates colonic inflammation in an IBD mouse model, implicating UTX's oxygen-sensitive demethylase activity in counteracting hypoxic inflammation.

Comparative Molecular and Biological Characteristic of the Systemic Inflammatory Response in Adult and Old Male Wistar Rats with Different Resistance to Hypoxia

Morphological, molecular, and biological features of the systemic inflammatory response induced by LPS administration were assessed in adult and old male Wistar rats with high and low resistance to hypoxia. In 6 h after LPS administration, mRNA expression levels of Hif1a, Vegf, Nfkb, and level of IL-1β protein in old rats were higher than in adult rats regardless of hypoxia tolerance. The morphometric study showed that the number of neutrophils in the interalveolar septa of the lungs was significantly higher in low-resistant adult and old rats 6 h after LPS administration. Thus, in old male Wistar rats, systemic inflammatory response is more pronounced than in adult rats and depends on the initial tolerance to hypoxia, which should be considered when developing new approaches to the therapy of systemic inflammatory response in individuals of different ages.

Hypoxia-Induced Signaling in Gut and Liver Pathobiology

Oxygen (O2) is essential for cellular metabolism and biochemical reactions. When the demand for O2 exceeds the supply, hypoxia occurs. Hypoxia-inducible factors (HIFs) are essential to activate adaptive and survival responses following hypoxic stress. In the gut (intestines) and liver, the presence of oxygen gradients or physiologic hypoxia is necessary to maintain normal homeostasis. While physiologic hypoxia is beneficial and aids in normal functions, pathological hypoxia is harmful as it exacerbates inflammatory responses and tissue dysfunction and is a hallmark of many cancers. In this review, we discuss the role of gut and liver hypoxia-induced signaling, primarily focusing on HIFs, in the physiology and pathobiology of gut and liver diseases. Additionally, we examine the function of HIFs in various cell types during gut and liver diseases, beyond intestinal epithelial and hepatocyte HIFs. This review highlights the importance of understanding hypoxia-induced signaling in the pathogenesis of gut and liver diseases and emphasizes the potential of HIFs as therapeutic targets.

Hypoxia-sensing by the Histone Demethylase UTX ( KDM6A ) Controls Colitogenic CD4 + T cell Fate and Mucosal Inflammation

Hypoxia is a feature of inflammatory conditions [e.g., inflammatory bowel disease (IBD)] and can exacerbate tissue damage in these diseases. To counteract hypoxia's deleterious effects, adaptive responses have evolved which protect against hypoxia-associated tissue injury. To date, much attention has focused on hypoxia-activated HIF (hypoxia-inducible factor) transcription factors in these responses. However, recent work has identified epigenetic regulators that are also oxygen-sensitive, but their role in adaptation to hypoxic inflammation is currently unclear. Here, we show that the oxygen-sensing epigenetic regulator UTX is a critical modulator of colitis severity. Unlike HIF transcription factors that act on gut epithelial cells, UTX functions in colitis through its effects on immune cells. Hypoxia results in decreased CD4 + T cell IFN-γ production and increased CD4 + regulatory T cells, and these findings are recapitulated by T cell-specific UTX deficiency. Hypoxia impairs the histone demethylase activity of UTX, and loss of UTX function leads to accumulation of repressive H3K27me3 epigenetic marks at IL12/STAT4 pathway genes ( Il12rb2, Tbx21, and Ifng ). In a colitis mouse model, T cell-specific UTX deletion ameliorates colonic inflammation, protects against weight loss, and increases survival. Together these findings implicate UTX's oxygen-sensitive histone demethylase activity in mediating protective, hypoxia-induced pathways in colitis.

Personalized redox medicine in inflammatory bowel diseases: an emerging role for HIF-1α and NRF2 as therapeutic targets

Inflammatory bowel diseases (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC), are intimately associated with inflammation and overproduction of reactive oxygen species (ROS). Temporal and inter-individual variabilities in disease activity and response to therapy pose significant challenges to diagnosis and patient care. Discovery and validation of truly integrative biomarkers would benefit from embracing redox metabolomics approaches with prioritization of central regulatory hubs. We here make a case for applying a personalized redox medicine approach that aims to selectively inhibit pathological overproduction and/or altered expression of specific enzymatic sources of ROS without compromising physiological function. To this end, improved 'clinical-omics integration' may help to better understand which particular redox signaling pathways are disrupted in what patient. Pharmacological interventions capable of activating endogenous antioxidant defense systems may represent viable therapeutic options to restore local/systemic redox status, with HIF-1α and NRF2 holding particular promise in this context. Achieving the implementation of clinically meaningful mechanism-based biomarkers requires development of easy-to-use, robust and cost-effective tools for secure diagnosis and monitoring of treatment efficacy. Ultimately, matching redox-directed pharmacological interventions to individual patient phenotypes using predictive biomarkers may offer new opportunities to break the therapeutic ceiling in IBD.

Hypoxia inducible factor prolyl hydroxylases in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic disease that is characterized by intestinal inflammation. Epithelial damage and loss of intestinal barrier function are believed to be the hallmark pathologies of the disease. In IBD, the resident and infiltrating immune cells consume much oxygen, rendering the inflamed intestinal mucosa hypoxic. In hypoxia, the hypoxia-inducible factor (HIF) is induced to cope with the lack of oxygen and protect intestinal barrier. Protein stability of HIF is tightly controlled by prolyl hydroxylases (PHDs). Stabilization of HIF through inhibition of PHDs is appearing as a new strategy of IBD treatment. Studies have shown that PHD-targeting is beneficial to the treatment of IBD. In this Review, we summarize the current understanding of the role of HIF and PHDs in IBD and discuss the therapeutic potential of targeting PHD-HIF pathway for IBD treatment.

Physiological hypoxia improves growth and functional differentiation of human intestinal epithelial organoids

Background

The epithelium in the colonic mucosa is implicated in the pathophysiology of various diseases, including inflammatory bowel diseases and colorectal cancer. Intestinal epithelial organoids from the colon (colonoids) can be used for disease modeling and personalized drug screening. Colonoids are usually cultured at 18-21% oxygen without accounting for the physiological hypoxia in the colonic epithelium (3% to <1% oxygen). We hypothesize that recapitulating the in vivo physiological oxygen environment (i.e., physioxia) will enhance the translational value of colonoids as pre-clinical models. Here we evaluate whether human colonoids can be established and cultured in physioxia and compare growth, differentiation, and immunological responses at 2% and 20% oxygen.

Methods

Growth from single cells to differentiated colonoids was monitored by brightfield images and evaluated with a linear mixed model. Cell composition was identified by immunofluorescence staining of cell markers and single-cell RNA-sequencing (scRNA-seq). Enrichment analysis was used to identify transcriptomic differences within cell populations. Pro-inflammatory stimuli induced chemokines and Neutrophil gelatinase-associated lipocalin (NGAL) release were analyzed by Multiplex profiling and ELISA. Direct response to a lower oxygen level was analyzed by enrichment analysis of bulk RNA sequencing data.

Results

Colonoids established in a 2% oxygen environment acquired a significantly larger cell mass compared to a 20% oxygen environment. No differences in expression of cell markers for cells with proliferation potential (KI67 positive), goblet cells (MUC2 positive), absorptive cells (MUC2 negative, CK20 positive) and enteroendocrine cells (CGA positive) were found between colonoids cultured in 2% and 20% oxygen. However, the scRNA-seq analysis identified differences in the transcriptome within stem-, progenitor- and differentiated cell clusters. Both colonoids grown at 2% and 20% oxygen secreted CXCL2, CXCL5, CXCL10, CXCL12, CX3CL1 and CCL25, and NGAL upon TNF + poly(I:C) treatment, but there appeared to be a tendency towards lower pro-inflammatory response in 2% oxygen. Reducing the oxygen environment from 20% to 2% in differentiated colonoids altered the expression of genes related to differentiation, metabolism, mucus lining, and immune networks.

Conclusions

Our results suggest that colonoids studies can and should be performed in physioxia when the resemblance to in vivo conditions is important.

Hypoxia-Inducible Factor 1-Alpha Stabilizers in the Treatment of Inflammatory Bowel Diseases: Oxygen as a Novel IBD Therapy?

Despite the significant advances in the medical armamentarium for inflammatory bowel diseases [IBD], current treatment options have notable limitations. Durable remission rates remain low, loss of response is common, administration routes are largely parenteral for novel biologics, and medication safety remains a concern. This explains an ongoing unmet need for safe medications with novel mechanisms of action that are administered orally. In line with these criteria, hypoxia-inducible factor [HIF]-1α stabilizers, acting via inhibition of prolyl hydroxylase enzymes, are emerging as an innovative therapeutic strategy. We herein review the mechanism of action and available clinical data for HIF-1α stabilizers and their potential place in the future IBD treatment algorithm.

The HIF-prolyl hydroxylases have distinct and nonredundant roles in colitis-associated cancer

Colitis-associated colorectal cancer (CAC) is a severe complication of inflammatory bowel disease (IBD). HIF-prolyl hydroxylases (PHD1, PHD2, and PHD3) control cellular adaptation to hypoxia and are considered promising therapeutic targets in IBD. However, their relevance in the pathogenesis of CAC remains elusive. We induced CAC in Phd1-/-, Phd2+/-, Phd3-/-, and WT mice with azoxymethane (AOM) and dextran sodium sulfate (DSS). Phd1-/- mice were protected against chronic colitis and displayed diminished CAC growth compared with WT mice. In Phd3-/- mice, colitis activity and CAC growth remained unaltered. In Phd2+/- mice, colitis activity was unaffected, but CAC growth was aggravated. Mechanistically, Phd2 deficiency (i) increased the number of tumor-associated macrophages in AOM/DSS-induced tumors, (ii) promoted the expression of EGFR ligand epiregulin in macrophages, and (iii) augmented the signal transducer and activator of transcription 3 and extracellular signal-regulated kinase 1/2 signaling, which at least in part contributed to aggravated tumor cell proliferation in colitis-associated tumors. Consistently, Phd2 deficiency in hematopoietic (Vav:Cre-Phd2fl/fl) but not in intestinal epithelial cells (Villin:Cre-Phd2fl/fl) increased CAC growth. In conclusion, the 3 different PHD isoenzymes have distinct and nonredundant effects, promoting (PHD1), diminishing (PHD2), or neutral (PHD3), on CAC growth.

Redox and Metabolic Regulation of Intestinal Barrier Function and Associated Disorders

The intestinal epithelium forms a physical barrier assembled by intercellular junctions, preventing luminal pathogens and toxins from crossing it. The integrity of tight junctions is critical for maintaining intestinal health as the breakdown of tight junction proteins leads to various disorders. Redox reactions are closely associated with energy metabolism. Understanding the regulation of tight junctions by cellular metabolism and redox status in cells may lead to the identification of potential targets for therapeutic interventions. In vitro and in vivo models have been utilized in investigating intestinal barrier dysfunction and in particular the free-living soil nematode, Caenorhabditis elegans, may be an important alternative to mammalian models because of its convenience of culture, transparent body for microscopy, short generation time, invariant cell lineage and tractable genetics.

Prolyl Hydroxylase Inhibition Mitigates Allograft Injury During Liver Transplantation

BACKGROUND

Ischemia and reperfusion injury (IRI) determines primary allograft function after liver transplantation (LT). Primary graft dysfunction (PGD) is associated with increased morbidity and impaired graft survival and can eventually progress to graft failure requiring retransplantation. Hypoxia-inducible transcription factor-prolyl hydroxylase containing enzymes (PHD1, PHD2, and PHD3) are molecular oxygen sensors, which control the adaptive hypoxia response through the hypoxia-inducible factor (HIF). In this study, we have investigated pharmacological activation of the HIF pathway through inhibition of PHDs as a strategy to reduce PGD after LT.

METHODS

Primary rat hepatocytes were isolated and the impact of the pan-PHD small-molecule inhibitor ethyl-3,4-dihydroxybenzoate (EDHB) on HIF-1 and its downstream target gene expression assessed. Subsequently, various rodent models of segmental warm liver ischemia and reperfusion and orthotopic LT were applied to study the impact of EDHB on normothermic or combined cold and warm liver IRI. Liver enzyme levels and histology were analyzed to quantify hepatic IRI.

RESULTS

In vitro, EDHB induced HIF-1 signaling and significantly upregulated its downstream target heme-oxygenase 1 in primary rat hepatocytes. In vivo, after establishment of the optimal EDHB pretreatment conditions in a murine IRI model, EDHB pretreatment significantly mitigated hepatic IRI after warm segmental liver ischemia and reperfusion and allograft injury after orthotopic LT in rats. Mechanistically, EDHB stabilized HIF-1 in the liver and subsequently increased hepatoprotective heme-oxygenase 1 levels, which correlated with reduced hepatic IRI in these models.

CONCLUSIONS

This proof-of-concept study establishes a strong therapeutic rationale for targeting PHDs with small-molecule inhibitors to mitigate PGD after LT.

The effect of HIF on metabolism and immunity

Cellular hypoxia occurs when the demand for sufficient molecular oxygen needed to produce the levels of ATP required to perform physiological functions exceeds the vascular supply, thereby leading to a state of oxygen depletion with the associated risk of bioenergetic crisis. To protect against the threat of hypoxia, eukaryotic cells have evolved the capacity to elicit oxygen-sensitive adaptive transcriptional responses driven primarily (although not exclusively) by the hypoxia-inducible factor (HIF) pathway. In addition to the canonical regulation of HIF by oxygen-dependent hydroxylases, multiple other input signals, including gasotransmitters, non-coding RNAs, histone modifiers and post-translational modifications, modulate the nature of the HIF response in discreet cell types and contexts. Activation of HIF induces various effector pathways that mitigate the effects of hypoxia, including metabolic reprogramming and the production of erythropoietin. Drugs that target the HIF pathway to induce erythropoietin production are now approved for the treatment of chronic kidney disease-related anaemia. However, HIF-dependent changes in cell metabolism also have profound implications for functional responses in innate and adaptive immune cells, and thereby heavily influence immunity and the inflammatory response. Preclinical studies indicate a potential use of HIF therapeutics to treat inflammatory diseases, such as inflammatory bowel disease. Understanding the links between HIF, cellular metabolism and immunity is key to unlocking the full therapeutic potential of drugs that target the HIF pathway.

Hypoxia-dependent changes in cellular metabolism have important implications for the effective functioning of multiple immune cell subtypes. This Review describes the inputs that shape the hypoxic response in individual cell types and contexts, and the implications of this response for cellular metabolism and associated alterations in immune cell function.

Hypoxia is a common feature of particular microenvironments and at sites of immunity and inflammation, resulting in increased activity of the hypoxia-inducible factor (HIF).

In addition to hypoxia, multiple inputs modulate the activity of the HIF pathway, allowing nuanced downstream responses in discreet cell types and contexts.

HIF-dependent changes in cellular metabolism mitigate the effects of hypoxia and ensure that energy needs are met under conditions in which oxidative phosphorylation is reduced.

HIF-dependent changes in metabolism also profoundly affect the phenotype and function of immune cells.

The immunometabolic effects of HIF have important implications for targeting the HIF pathway in inflammatory disease.

Vitamin D Receptor-Dependent Protective Effect of Moderate Hypoxia in a Mouse Colitis Model

Although hypoxia is important for maintaining the intestinal barrier, its effect on the barrier during acute colitis and the underlying mechanisms are not fully understood. To explore the influence of hypoxia in dextran sulfate sodium (DSS)-induced colitis mice and the role of hypoxia-inducible factor (HIF) and vitamin D receptor (VDR) in the process. Colitis mice were subjected to hypoxia to detect intestinal barrier function changes. And the mechanisms were explored in vitro. First, compared with colitis mice without hypoxia stimulation, those with hypoxia stimulation showed significantly decreased pathological damage and improved permeability of the intestinal barrier. The expression of tight junction proteins (occludin, ZO-1), HIF-1α as well as VDR was up-regulated in colitis mice with hypoxia stimulation. However, in VDR gene knockout (KO)colitis mice, hypoxia treatment showed no protective effect, suggesting the VDR dependency of this effect. Similarly although hypoxia stimulation could enhance the single-layer epithelial transmembrane electrical resistance in DLD-1 and NCM460 cells, these effects disappeared in VDR-knockdown cells. Furthermore, over-expression of HIF-1α in DLD-1 and NCM460 increased the expression of VDR, whereas HIF-1α-knockdown reduced the VDR expression directly. Chromatin immunoprecipitation and luciferase assays confirmed that HIF-1α can bind to the promoter region of the VDR gene under hypoxia. Finally, compared with their wild-type siblings, VDR-KO mice showed reduced abundance of anaerobic bacteria and SCFA-producing bacteria. Hypoxia was protective against DSS-induced colitis, and VDR is instrumental in it. Furthermore, HIF-1α-VDR mediates the effect of hypoxia on the barrier function. Moreover, intestinal flora may be an important link between hypoxia and VDR.

Eosinophils, Hypoxia-Inducible Factors, and Barrier Dysfunction in Functional Dyspepsia

Functional dyspepsia (FD) is a highly prevalent disorder of gut-brain interaction (DGBI), previously known as a functional gastrointestinal disorder. Characterized by early satiety, postprandial fullness, and/or epigastric pain or burning, diagnosis depends on positive symptomatology and exclusion of obvious structural diseases. A subtle inflammatory phenotype has been identified in FD patients, involving an increase in duodenal mucosal eosinophils, and imbalances in the duodenal gut microbiota. A dysregulated epithelial barrier has also been well described in FD and is thought to be a contributing factor to the low-grade duodenal inflammation observed, however the mechanisms underpinning this are poorly understood. One possible explanation is that alterations in the microbiota and increased immune cells can result in the activation of cellular stress response pathways to perpetuate epithelial barrier dysregulation. One such cellular response pathway involves the stabilization of hypoxia-inducible factors (HIF). HIF, a transcriptional protein involved in the cellular recognition and adaptation to hypoxia, has been identified as a critical component of various pathologies, from cancer to inflammatory bowel disease (IBD). While the contribution of HIF to subtle inflammation, such as that seen in FD, is unknown, HIF has been shown to have roles in regulating the inflammatory response, particularly the recruitment of eosinophils, as well as maintaining epithelial barrier structure and function. As such, we aim to review our present understanding of the involvement of eosinophils, barrier dysfunction, and the changes to the gut microbiota including the potential pathways and mechanisms of HIF in FD. A combination of PubMed searches using the Mesh terms functional dyspepsia, functional gastrointestinal disorders, disorders of gut-brain interaction, duodenal eosinophilia, barrier dysfunction, gut microbiota, gut dysbiosis, low-grade duodenal inflammation, hypoxia-inducible factors (or HIF), and/or intestinal inflammation were undertaken in the writing of this narrative review to ensure relevant literature was included. Given the findings from various sources of literature, we propose a novel hypothesis involving a potential role for HIF in the pathophysiological mechanisms underlying FD.