Disturbance of Hypoxia Response and Its Implications in Kidney Diseases

Rapid evaluation of PHD2 inhibitory activity of natural products based on capillary electrophoresis online stacking strategy

Prolyl hydroxylase domain 2 (PHD2) is an important enzyme in the human body that perceives changes in oxygen concentration and regulates response in hypoxic environments. Evaluation of PHD2 inhibitory activity of natural products is crucial for drug development of hypoxia related diseases. At present, the detection of low concentration of α-ketoglutaric acid (the substrate of PHD2 enzymatic reaction) requires derivatization reactions or sample pretreatment, which undoubtedly increases the workload of PHD2 inhibitory activity evaluation. In this paper, a direct detection approach of α-ketoglutaric acid was established by using the online stacking strategy of capillary electrophoresis to evaluate the PHD2 inhibitory activity of natural products. Under optimized conditions, detection of a single sample can be achieved within 2 min. By calculation, the intraday precision RSD of the apparent electrophoretic mobility and peak areas of α-ketoglutaric acid are 0.92 % and 0.79 %, respectively, and the interday RSD were 1.27 % and 0.96 % respectively. The recoveries of the present approach were 97.9-105.2 %, and the LOQ and LOD were 2.0 μM and 5.0 μM, respectively. Furthermore, this approach was applied for the evaluation of inhibitory activity of PHD2 for 13 natural products, and PHD2 inhibitory activity of salvianolic acid A was firstly reported. The present work not only realizes evaluation of PHD2 inhibitory activity through direct detection of α-ketoglutaric acid, but also provides technical support for the discovery of potential drug molecules in hypoxia related diseases.

Disturbances in Nitric Oxide Cycle and Related Molecular Pathways in Clear Cell Renal Cell Carcinoma

It is important to note that maintaining adequate levels of nitric oxide (NO), the turnover, and the oxidation level of nitrogen are essential for the optimal progression of cellular processes, and alterations in the NO cycle indicate a crucial step in the onset and progression of multiple diseases. Cellular accumulation of NO and reactive nitrogen species in many types of tumour cells is expressed by an increased susceptibility to oxidative stress in the tumour microenvironment. Clear cell renal cell carcinoma (ccRCC) is a progressive metabolic disease in which tumour cells can adapt to metabolic reprogramming to enhance NO production in the tumour space. Understanding the factors governing NO biosynthesis metabolites in ccRCC represents a relevant, valuable approach to studying NO-based anticancer therapy. Exploring the molecular processes mediated by NO, related disturbances in molecular pathways, and NO-mediated signalling pathways in ccRCC could have significant therapeutic implications in managing and treating this condition.

Activation of HIF-1α C-terminal transactivation domain protects against hypoxia-induced kidney injury through hexokinase 2-mediated mitophagy

The transcription factor hypoxia-inducible factor-1α (HIF-1α), as a master regulator of adaptive responses to hypoxia, possesses two transcriptional activation domains [TAD, N-terminal (NTAD), and C-terminal (CTAD)]. Although the roles of HIF-1α NTAD in kidney diseases have been recognized, the exact effects of HIF-1α CTAD in kidney diseases are poorly understood. Here, two independent mouse models of hypoxia-induced kidney injury were established using HIF-1α CTAD knockout (HIF-1α CTAD^-/-) mice. Furthermore, hexokinase 2 (HK2) and mitophagy pathway are modulated using genetic and pharmacological methods, respectively. We demonstrated that HIF-1α CTAD^-/- aggravated kidney injury in two independent mouse models of hypoxia-induced kidney injury, including ischemia/reperfusion-induced kidney injury and unilateral ureteral obstruction-induced nephropathy. Mechanistically, we found that HIF-1α CTAD could transcriptionally regulate HK2 and subsequently ameliorate hypoxia-induced tubule injury. Furthermore, it was found that HK2 deficiency contributed to severe renal injury through mitophagy inhibition, while mitophagy activation using urolithin A could significantly protect against hypoxia-induced kidney injury in HIF-1α C-TAD^-/- mice. Our findings suggested that the HIF-1α CTAD-HK2 pathway represents a novel mechanism of kidney response to hypoxia, which provides a promising therapeutic strategy for hypoxia-induced kidney injury.

ARS Forum Oxygen Sensing

Molecular oxygen is often represented as a double-edged sword, essential to sustain oxidative phosphorylation that provides the bulk of the cell biological energy, yet toxic. In the current geological era, its proportion in the atmosphere happens to be 20.93%-20.95%, but in past eras, it fluctuated within the 0%-30% range, with different forms of life that could adapt successfully even by using alternative redox sources as hydrogen sulfide. Actually, humans may have lost the ability to adapt to oxygen levels departing consistently from 20.93% to 20.95%. Consequently, either hypoxia or hyperoxia represents potentially lethal situations. Yet, they are more common than suspected. Hypoxia is found in physiological (high altitude, commercial flights, prebirth environment, and physical exercise) and pathological (inflammation, solid cancers, ischemia, as well as in cardiopulmonary, kidney, and neurodegenerative diseases) contexts, whereas hyperoxia, although less frequent, is the most used therapy in pulmonary patients and during anesthesia. The Forum "Oxygen Sensing" contains contributions aimed at clarifying the complex mechanisms underlying the responses to too much and too little oxygen at molecular, cellular, tissue, and body levels, highlighting the oxygen-sensing mechanisms in various districts of the organism. The translational interest of this Forum invests the modulation of the oxygen-sensing activity and sensitivity as a therapeutic perspective in the treatment of several diseases. Antioxid. Redox Signal. 37, 863-866.

Hypoxia-Nitric Oxide Axis and the Associated Damage Molecular Pattern in Cutaneous Melanoma

Hypoxia was intensively studied in cancer during the last few decades, being considered a characteristic of the tumor microenvironment. The aim of the study was to evaluate the capacity of tumor cells to adapt to the stress generated by limited oxygen tissue in cutaneous melanoma. We developed a case-control prospective study that included 52 patients with cutaneous melanoma and 35 healthy subjects. We focused on identifying and monitoring hypoxia, the dynamic of nitric oxide (NO) serum metabolites and posttranslational metabolic disorders induced by NO signaling according to the clinical, biological and tumoral characteristics of the melanoma patients. Our study showed high levels of hypoxia-inducible factor-1a (HIF-1a) and hypoxia-inducible factor-2a (HIF-2a) in the melanoma patients. Hypoxia-inducible factors (HIFs) control the capacity of tumor cells to adapt to low levels of oxygen. Hypoxia regulated the nitric oxide synthase (NOS) expression and activity. In the cutaneous melanoma patients, disorders in NO metabolism were detected. The serum levels of the NO metabolites were significantly higher in the melanoma patients. NO signaling influenced the tumor microenvironment by modulating tumoral proliferation and sustaining immune suppression. Maintaining NO homeostasis in the hypoxic tumoral microenvironment could be considered a future therapeutic target in cutaneous melanoma.