The functional interplay between the HIF pathway and the ubiquitin system – more than a one-way road

The hypoxia inducible factor (HIF) pathway and the ubiquitin system represent major cellular processes that are involved in the regulation of a plethora of cellular signaling pathways and tissue functions. The ubiquitin system controls the ubiquitination of proteins, which is the covalent linkage of one or several ubiquitin molecules to specific targets. This ubiquitination is catalyzed by approximately 1000 different E3 ubiquitin ligases and can lead to different effects, depending on the type of internal ubiquitin chain linkage. The best-studied function is the targeting of proteins for proteasomal degradation. The activity of E3 ligases is antagonized by proteins called deubiquitinases (or deubiquitinating enzymes), which negatively regulate ubiquitin chains. This is performed in most cases by the catalytic removal of these chains from the targeted protein. The HIF pathway is regulated in an oxygen-dependent manner by oxygen-sensing hydroxylases. Covalent modification of HIFα subunits leads to the recruitment of an E3 ligase complex via the von Hippel-Lindau (VHL) protein and the subsequent polyubiquitination and proteasomal degradation of HIFα subunits, demonstrating the regulation of the HIF pathway by the ubiquitin system. This unidirectional effect of an E3 ligase on the HIF pathway is the beststudied example for the interplay between these two important cellular processes. However, additional regulatory mechanisms of the HIF pathway through the ubiquitin system are emerging and, more recently, also the reciprocal regulation of the ubiquitin system through components of the HIF pathway. Understanding these mechanisms and their relevance for the activity of each other is of major importance for the comprehensive elucidation of the oxygen-dependent regulation of cellular processes. This review describes the current knowledge of the functional bidirectional interplay between the HIF pathway and the ubiquitin system on the protein level

Integration, Familie und Gender

Thiessen B. Integration, Familie und Gender. In: Pickel G, Decker O, Kailitz S, Röder A, Schulze Wessel J, eds. Handbuch Integration. Wiesbaden: Springer Fachmedien Wiesbaden; 2020: 1-11

Migration, Integration und Gesundheit

Günther W, Reiter R, Schmidt PF. Migration, Integration und Gesundheit. In: Pickel G, Decker O, Kailitz S, Röder A, Schulze Wessel J, eds. Handbuch Integration. Living reference work, continuously updated edition. Wiesbaden: Springer VS; 2019

Mycotic Antimicrobial Localized Injection A Randomized Clinical Trial Evaluating Intrastromal Injection of Voriconazole

PURPOSE:To determine if there is a benefit to adjuvant intrastromal voriconazole (ISV) injections for primary treatment of filamentous fungal keratitis. DESIGN:Outcome-masked, randomized controlled clinical trial. PARTICIPANTS:Patients with moderate vision loss resulting from a smear-positive fungal ulcer. METHODS:Study eyes were randomized to topical natamycin plus ISV injection versus topical natamycin alone. MAIN OUTCOME MEASURES:The primary outcome of the trial was microbiological cure on 3-day repeat culture analysis. Secondary outcomes included microbiological cure on 7-day repeat culture analysis; 3-week and 3-month best spectacle-corrected visual acuity; infiltrate or scar size or both; rate of perforation; therapeutic penetrating keratoplasty (TPK); and other adverse events. RESULTS:A total of 151 patients with smear-positive ulcers were screened and 70 were enrolled at Aravind Eye Hospital, Pondicherry, India. Baseline cultures grew Fusarium in 19 samples (27%), Aspergillus in 17 samples (24%), and other filamentous fungi in 19 samples (27%) and showed negative results in 13 samples (19%). Those randomized to ISV injection had 1.82 times the odds of 3-day culture positivity after controlling for baseline culture status (95% confidence interval [CI], 0.65-5.23; P = 0.26, bias-corrected logistic regression) and 1.98 times the odds of positive 7-day culture results, after controlling for baseline culture status (95% CI, 0.69-5.91; P = 0.20, bias-corrected logistic regression). Those randomized to ISV injection showed 0.5 logMAR lines (approximately 0.5 Snellen lines) of decreased visual acuity (95% CI, -2.6 to 3.6 lines; P = 0.75) and 0.55 mm worse infiltrate or scar size or both at 3 months after controlling for baseline values (95% CI, -0.13 to 1.25; P = 0.11). Intrastromal voriconazole injections showed a 2.85-fold increased hazard of perforation after controlling for baseline infiltrate depth (95% CI, 0.76-10.75; P = 0.12) but no difference in the rate of TPK (hazard ratio, 0.95; 95% CI, 0.44-2.04; P = 0.90). CONCLUSIONS:There seems to be no benefit to adding ISV injections to topical natamycin in the primary treatment of moderate to severe filamentous fungal ulcers. Studies consistently suggest that voriconazole has a limited role in the treatment of filamentous fungal ulcers

HIF hydroxylase inhibitors decrease cellular oxygen consumption depending on their selectivity

Pharmacologic HIF hydroxylase inhibitors (HIs) are effective for the treatment of anemia in chronic kidney disease patients and may also be beneficial for the treatment of diseases such as chronic inflammation and ischemia-reperfusion injury. The selectivities of many HIs for HIF hydroxylases and possible off-target effects in cellulo are unclear, delaying the translation from preclinical studies to clinical trials. We developed a novel assay that discriminates between the inhibition of HIF-α prolyl-4-hydroxylase domain (PHD) enzymes and HIF-α asparagine hydroxylase factor inhibiting HIF (FIH). We characterized 15 clinical and preclinical HIs, categorizing them into pan-HIF-α hydroxylase (broad spectrum), PHD-selective, and FIH-selective inhibitors, and investigated their effects on HIF-dependent transcriptional regulation, erythropoietin production, and cellular energy metabolism. While energy homeostasis was generally maintained following HI treatment, the pan-HIs led to a stronger increase in pericellular pO2 than the PHD/FIH-selective HIs. Combined knockdown of FIH and PHD-selective inhibition did not further increase pericellular pO2 . Hence, the additional increase in pericellular pO2 by pan- over PHD-selective HIs likely reflects HIF hydroxylase independent off-target effects. Overall, these analyses demonstrate that HIs can lead to oxygen redistribution within the cellular microenvironment, which should be considered as a possible contributor to HI effects in the treatment of hypoxia-associated diseases

Oxygen-dependent bond formation with FIH regulates the activity of the client protein OTUB1

Protein:protein interactions are the basis of molecular communication and are usually of transient non-covalent nature, while covalent interactions other than ubiquitination are rare. For cellular adaptations, the cellular oxygen and peroxide sensor factor inhibiting HIF (FIH) confers oxygen and oxidant stress sensitivity to the hypoxia inducible factor (HIF) by asparagine hydroxylation. We investigated whether FIH contributes to hypoxia adaptation also through other mechanisms and identified a hypoxia sensitive, likely covalent, bond formation by FIH with several client proteins, including the deubiquitinase ovarian tumor domain containing ubiquitin aldehyde binding protein 1 (OTUB1). Biochemical analyses were consistent with a co-translational amide bond formation between FIH and OTUB1, occurring within mammalian and bacterial cells but not between separately purified proteins. Bond formation is catalysed by FIH and highly dependent on oxygen availability in the cellular microenvironment. Within cells, a heterotrimeric complex is formed, consisting of two FIH and one covalently linked OTUB1. Complexation of OTUB1 by FIH regulates OTUB1 deubiquitinase activity. Our findings reveal an alternative mechanism for hypoxia adaptation with remarkably high oxygen sensitivity, mediated through covalent protein-protein interactions catalysed by an asparagine modifying dioxygenase

Acceptability, Feasibility, and Quality of Telehealth for Adolescent Health Care Delivery During the COVID-19 Pandemic: Cross-sectional Study of Patient and Family Experiences

BackgroundData regarding the acceptability, feasibility, and quality of telehealth among adolescents and young adults (AYA) and their parents and caregivers (caregivers) are lacking. ObjectiveThe aim of this study was to assess the noninferiority of telehealth versus in-person visits by comparing acceptability with respect to efficiency, effectiveness, equity, patient-centeredness, and confidentiality. MethodsCross-sectional web-based surveys were sent to caregivers and AYA following video visits within an Adolescent Medicine subspecialty clinic in May-July 2020. Proportions of AYA and caregivers who rated telehealth as noninferior were compared using chi-squared tests. Feasibility was assessed via items measuring technical difficulties. Deductive thematic analysis using the Institute of Medicine dimensions of health care quality was used to code open-ended question responses. ResultsSurvey response rates were 20.5% (55/268) for AYA and 21.8% (123/563) for caregivers. The majority of the respondents were White cisgender females. Most AYA and caregivers rated telehealth as noninferior to in-person visits with respect to confidentiality, communication, medication management, and mental health care. A higher proportion of AYA compared to caregivers found telehealth inferior with respect to confidentiality (11/51, 22% vs 3/118, 2.5%, P<.001). One-quarter (14/55) of the AYA patients and 31.7% (39/123) of the caregivers reported technical difficulties. The dominant themes in the qualitative data included advantages of telehealth for efficiency and equity of health care delivery. However, respondents’ concerns included reduced safety and effectiveness of care, particularly for patients with eating disorders, owing to lack of hands-on examinations, collection of vital signs, and laboratory testing. ConclusionsTelehealth was highly acceptable among AYA and caregivers. Future optimization should include improving privacy, ameliorating technical difficulties, and standardizing at-home methods of obtaining patient data to assure patient safety