Low-Dose Near-Infrared Light-Activated Mitochondria-Targeting Photosensitizers for PDT Cancer Therapy

Phthalocyanines (Pcs) are promising candidates for photodynamic therapy (PDT) due to their absorption in the phototherapeutic window. However, the highly aromatic Pc core leads to undesired aggregation and decreased reactive oxygen species (ROS) production. Therefore, short PEG chain functionalized A₃B type asymmetric Pc photosensitizers (PSs) were designed in order to decrease aggregation and increase the aqueous solubility. Here we report the synthesis, characterization, optical properties, cellular localization, and cytotoxicity of three novel Pc-based agents (LC31, MLC31, and DMLC31Pt). The stepwise functionalization of the peripheral moieties has a strong effect on the distribution coefficient (logP), cellular uptake, and localization, as well as photocytotoxicity. Additional experiments have revealed that the presence of the malonic ester moiety in the reported agent series is indispensable in order to induce photocytotoxicity. The best-performing agent, MLC31, showed mitochondrial targeting and an impressive phototoxic index (p.i.) of 748 in the cisplatin-resistant A2780/CP70 cell line, after a low-dose irradiation of 6.95 J/cm². This is the result of a high photocytotoxicity (IC₅₀ = 157 nM) upon irradiation with near-infrared (NIR) light, and virtually no toxicity in the dark (IC₅₀ = 117 μM). Photocytotoxicity was subsequently determined under hypoxic conditions. Additionally, a preliminarily pathway investigation of the mitochondrial membrane potential (MMP) disruption and induction of apoptosis by MLC31 was carried out. Our results underline how agent design involving both hydrophilic and lipophilic peripheral groups may serve as an effective way to improve the PDT efficiency of highly aromatic PSs for NIR light-mediated cancer therapy.

Fate-mapping of erythropoietin-producing cells in mouse models of hypoxaemia and renal tissue remodelling reveals repeated recruitment and persistent functionality

Aim

Fibroblast‐like renal erythropoietin (Epo) producing (REP) cells of the corticomedullary border region “sense” a decrease in blood oxygen content following anaemia or hypoxaemia. Burst‐like transcription of Epo during tissue hypoxia is transient and is lost during fibrotic tissue remodelling, as observed in chronic kidney disease. The reason for this loss of Epo expression is under debate. Therefore, we tested the hypothesis that REP cell migration, loss and/or differentiation may cause Epo inhibition.

Methods

Using a reporter mouse that allows permanent labelling of active REP cells at any given time point, we analysed the spatiotemporal fate of REP cells following their initial hypoxic recruitment in models of hypoxaemia and renal tissue remodelling.

Results

In long‐term tracing experiments, tagged REP reporter cells neither died, proliferated, migrated nor transdifferentiated into myofibroblasts. Approximately 60% of tagged cells re‐expressed Epo upon a second hypoxic stimulus. In an unilateral model of tissue remodelling, tagged cells proliferated and ceased to produce Epo before a detectable increase in myofibroblast markers. Treatment with a hypoxia‐inducible factor (HIF) stabilizing agent (FG‐4592/roxadustat) re‐induced Epo expression in the previously active REP cells of the damaged kidney to a similar extent as in the contralateral healthy kidney.

Conclusions

Rather than cell death or differentiation, these results suggest cell‐intrinsic transient inhibition of Epo transcription: following long‐term dormancy, REP cells can repeatedly be recruited by tissue hypoxia, and during myofibrotic tissue remodelling, dormant REP cells are efficiently rescued by a pharmaceutic HIF stabilizer, demonstrating persistent REP cell functionality even during phases of Epo suppression.

Distal and proximal hypoxia response elements cooperate to regulate organ-specific erythropoietin gene expression

While it is well-established that distal hypoxia response elements (HREs) regulate hypoxia-inducible factor (HIF) target genes such as erythropoietin (Epo), an interplay between multiple distal and proximal (promoter) HREs has not been described so far. Hepatic Epo expression is regulated by a HRE located downstream of the EPO gene, but this 3' HRE is dispensable for renal EPO gene expression. We previously identified a 5' HRE and could show that both HREs direct exogenous reporter gene expression. Here, we show that whereas in hepatic cells the 3' but not the 5' HRE is required, in neuronal cells both the 5' and 3' HREs contribute to endogenous Epo induction. Moreover, two novel putative HREs were identified in the EPO promoter. In hepatoma cells HIF interacted mainly with the distal 3' HRE, but in neuronal cells HIF most strongly bound the promoter, to a lesser extent the 3' HRE, and not at all the 5' HRE. Interestingly, mutation of either of the two distal HREs abrogated HIF binding to the 3' and promoter HREs. These results suggest that a canonical functional HRE can recruit multiple, not necessarily HIF, transcription factors to mediate HIF binding to different distant HREs in an organ-specific manner.

Device profile of the Bonebridge bone conduction implant system in hearing loss: an overview of its safety and efficacy

INTRODUCTION

The Bonebridge is an active transcutaneous semi-implantable bone conduction hearing device suitable for several types of hearing loss. It has unique benefits over some more established technologies. It consists of an internal active implant and an external sound processor. It was first launched in 2012, with a newer model released in late 2019.

AREAS COVERED

The structure and features of the device are described. Indications, audiological criteria, and contraindications to implantation are discussed. The planning and procedure of implantation surgery are also described. Research outlining the outcomes of implant use and risk of adverse events is highlighted.

EXPERT OPINION

The evidence included in this article demonstrates the successful audiological outcomes and patient satisfaction with Bonebridge implantation. The rate of adverse events following surgery is low and compares well with other devices which may be considered for Bonebridge candidates. The device should be considered as an option for suitable candidates and in many cases may be the better option available, given the low incidence of skin complications and the absence of a skin penetrating abutment. Future advances are likely to affect sound processor technology, connectivity, and possibly further reduction in implant size and gain.

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.

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FIH forms a (likely amide) bond with client proteins.

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Bond formation is highly hypoxia sensitive and occurs co-translationally.

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FIH forms a heterotrimer with the client protein OTUB1 (FIH₂OTUB1₁).

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Complex formation between OTUB1 and FIH regulates OTUB1 deubiquitinase activity.

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Bond formation by hydroxylases is an alternative mechanism for hypoxia adaptation.

Quality of Life Outcomes following Treatment of Hypopharyngeal Cancer

Quality of life (QoL) is an important consideration in the management of individuals with head and neck cancer. The poor prognosis and significant impact of treatment modalities on function of the salivary glands, larynx and pharynx combine to make hypopharyngeal carcinoma a particularly challenging condition to treat. The impact of diagnosis and treatment on health related QoL is substantial. There is increased understanding that organ preservation does not necessarily correlate with function preservation as was previously expected. The impact on QoL, of chemoradiotherapy (CRT) or surgery, must be taken into account when managing individuals and deciding on treatment. Several QoL tools have been developed to understand the subjective consequences of functional impairment. The number and quality of studies specifically for hypopharyngeal carcinoma are low. The effects on QoL differ for surgery and CRT, as one would expect, but there are no demonstrable significant differences in most domains. Those treated with CRT show higher levels of dry mouth and sticky saliva, while those patients who have undergone surgery report greater levels of sensory disturbance. Significant differences were not noted in speech outcomes or global (general) health scores. The psychological morbidity and lack of good coping strategies are thought to play an important role in the high suicide rates of these patients (12-fold higher than the average population in the USA). Large, long-term, longitudinal studies of patients surviving treatment, answering both general and disease-specific questionnaires are required to direct clinicians towards the least morbid treatment strategies. The ability to cope and the availability of emotional support probably have a greater impact on subjective QoL than the functional outcomes of treatment.

Hypoxia ameliorates intestinal inflammation through NLRP3/mTOR downregulation and autophagy activation

Hypoxia regulates autophagy and nucleotide-binding oligomerization domain receptor, pyrin domain containing (NLRP)3, two innate immune mechanisms linked by mutual regulation and associated to IBD. Here we show that hypoxia ameliorates inflammation during the development of colitis by modulating autophagy and mammalian target of rapamycin (mTOR)/NLRP3 pathway. Hypoxia significantly reduces tumor necrosis factor α, interleukin (IL)-6 and NLRP3 expression, and increases the turnover of the autophagy protein p62 in colon biopsies of Crohn’s disease patients, and in samples from dextran sulfate sodium-treated mice and Il-10^−/− mice. In vitro, NF-κB signaling and NLRP3 expression are reduced through hypoxia-induced autophagy. We also identify NLRP3 as a novel binding partner of mTOR. Dimethyloxalylglycine-mediated hydroxylase inhibition ameliorates colitis in mice, downregulates NLRP3 and promotes autophagy. We suggest that hypoxia counteracts inflammation through the downregulation of the binding of mTOR and NLRP3 and activation of autophagy.

Hypoxia and HIF-1α activation are protective in mouse models of colitis, and the latter regulates autophagy. Here Cosin-Roger et al. show that hypoxia ameliorates intestinal inflammation in Crohn’s patients and murine colitis models by inhibiting mTOR/NLRP3 pathway and promoting autophagy.

Hypoxia attenuates the proinflammatory response in colon cancer cells by regulating IκB

Two main features common to all solid tumors are tissue hypoxia and inflammation, both of which cause tumor progression, metastasis, therapy resistance and increased mortality. Chronic inflammation is associated with increased cancer risk, as demonstrated for inflammatory bowel disease patients developing colon cancer. However, the interplay between hypoxia and inflammation on the molecular level remains to be elucidated. We found that MC-38 mouse colon cancer cells contain functional hypoxic (HIF-1α) and inflammatory (p65/RelA) signaling pathways. In contrast to cells of the myeloid lineage, HIF-1α levels remained unaffected in MC-38 cells treated with LPS, and hypoxia failed to induce NF-κB. A similar regulation of canonical HIF and NF-κB target genes confirmed these results. RNA deep sequencing of HIF-1α and p65/RelA knock-down cells revealed that a surprisingly large fraction of HIF target genes required p65/RelA for hypoxic regulation and a number of p65/RelA target genes required HIF-1α for proinflammatory regulation, respectively. Hypoxia attenuated the inflammatory response to LPS by inhibiting nuclear translocation of p65/RelA independently of HIF-1α, which was associated with enhanced IκBα levels and decreased IKKβ phosphorylation. These data demonstrate that the interaction between hypoxic and inflammatory signaling pathways needs to be considered when designing cancer therapies targeting HIF or NF-κB.

Hypoxia enhances lipid uptake in macrophages: role of the scavenger receptors Lox1, SRA, and CD36

OBJECTIVES

The core of advanced atherosclerotic plaques turns hypoxic as the arterial wall thickens and oxygen diffusion capacity becomes impaired. Macrophage-derived foam cells play a pivotal role in atherosclerotic plaque formation by expressing scavenger receptors that regulate lipid uptake. However, the role of hypoxia in scavenger receptor regulation remains incompletely understood.

METHODS AND RESULTS

Using RT-qPCR, flow cytometry and immunoblotting, we found that mRNA and protein expression levels of the scavenger receptor A (SRA) and the cluster of differentiation 36 (CD36) were upregulated by oxidized low-density lipoprotein (oxLDL), but decreased following exposure of macrophages to hypoxia. In contrast, lectin-like oxLDL receptor (Lox-1) mRNA and protein levels were upregulated under hypoxic conditions. Flow cytometry confirmed the increased lipid content in macrophages after exposure to 0.2% oxygen and the hypoxia-mimetic dimethyloxalylglycine (DMOG). Antibody-mediated blocking of Lox-1 receptor decreased the hypoxic induction of oxLDL uptake and lipid content. RNAi-mediated knock-down of hypoxia-inducible factor (HIF)-1α in macrophages attenuated the hypoxic induction of Lox-1.

CONCLUSIONS

Hypoxia increases lipid uptake into macrophages and differentially regulates the expression of oxLDL receptors. Lox-1 plays a major role in hypoxia-induced foam cell formation which is, at least in part, mediated by HIF-1α.

To drain or not to drain - management of pediatric deep neck abscesses: a case-control study

Optimal management of deep neck abscesses has been the subject of debate for more than a century: surgical drainage has been the mainstay of treatment, but recently many centres have reported successful non-operative management in selected cases.

OBJECTIVES

Our objective was to review the management of deep neck abscesses in our institution and to identify characteristics that would predict successful non-operative management.

METHODS

A retrospective chart review from January 2001 to August 2010 was performed. Children up to age fifteen years with a CT-confirmed diagnosis of retropharyngeal or parapharyngeal abscess were included. A case-control study of small deep space neck abscesses (≤ 25 mm maximal diameter) was performed, comparing antibiotic treatment alone with antibiotics plus abscess drainage.

RESULTS

54 children met the inclusion criteria, of whom half had abscesses ≤ 25 mm diameter. Younger children within the group with smaller abscesses were more likely to need surgical drainage (p<0.05). Of 13 children requiring operative management, ten underwent a period of antibiotic treatment and observation prior to surgery, eight (80%) had fever beyond 48 h compared with three (23%) in the non-surgical group (p<0.01). 27 children had an abscess > 25 mm diameter on CT scan, four (15%) of whom responded quickly to antibiotics and were managed non-operatively, while the rest underwent surgery. There were no significant differences between the surgical and non-surgical group characteristics with larger abscesses.

CONCLUSION

High dose intravenous antibiotics are an effective treatment for deep space neck abscesses and may obviate the need for surgical drainage, particularly in smaller abscesses. Children who do not respond quickly to antibiotics are more likely to require surgery to achieve resolution. Children with larger abscesses may respond to antibiotic therapy alone but should be closely observed. A trial of high dose intravenous antibiotics in stable children with close observation is warranted as first line treatment, especially for small deep space neck abscesses.

Substrate preference and phosphatidylinositol monophosphate inhibition of the catalytic domain of the Per-Arnt-Sim domain kinase PASKIN

The Per-Arnt-Sim (PAS) domain serine/threonine kinase PASKIN, or PAS kinase, links energy flux and protein synthesis in yeast, regulates glycogen synthesis and protein translation in mammals, and might be involved in insulin regulation in the pancreas. According to the current model, binding of a putative ligand to the PAS domain disinhibits the kinase domain, leading to PASKIN autophosphorylation and increased kinase activity. To date, only synthetic but no endogenous PASKIN ligands have been reported. In the present study, we identified a number of novel PASKIN kinase targets, including ribosomal protein S6. Together with our previous identification of eukaryotic elongation factor 1A1, this suggests a role for PASKIN in the regulation of mammalian protein translation. When searching for endogenous PASKIN ligands, we found that various phospholipids can bind PASKIN and stimulate its autophosphorylation. Interestingly, the strongest binding and autophosphorylation was achieved with monophosphorylated phosphatidylinositols. However, stimulated PASKIN autophosphorylation did not correlate with ribosomal protein S6 and eukaryotic elongation factor 1A1 target phosphorylation. Although autophosphorylation was enhanced by monophosphorylated phosphatidylinositols, di- and tri-phosphorylated phosphatidylinositols inhibited autophosphorylation. By contrast, target phosphorylation was always inhibited, with the highest efficiency for di- and tri-phosphorylated phosphatidylinositols. Because phosphatidylinositol monophosphates were found to interact with the kinase rather than with the PAS domain, these data suggest a multiligand regulation of PASKIN activity, including a still unknown PAS domain binding/activating ligand and kinase domain binding modulatory phosphatidylinositol phosphates.

The PAS-domain kinase PASKIN: a new sensor in energy homeostasis

The PAS domain kinase PASKIN, also termed PAS kinase or PASK, is an evolutionarily conserved potential sensor kinase related to the heme-based oxygen sensors of nitrogen-fixing bacteria. In yeast, the two PASKIN homologs link energy flux and protein synthesis following specific stress conditions. In mammals, PASKIN may regulate glycogen synthesis and protein translation. Paskin knock-out mice do not show any phenotype under standard animal husbandry conditions. Interestingly, these mice seem to be protected from the symptoms of the metabolic syndrome when fed a high-fat diet. Energy turnover might be increased in specific PASKIN-deficient cell types under distinct environmental conditions. According to the current model, binding of a putative ligand to the PAS domain disinhibits the kinase domain and activates PASKIN auto- and target phosphorylation. Future research needs to be conducted to elucidate the nature of the putative ligand and the molecular mechanisms of downstream signalling by PASKIN.

Regulated function of the prolyl-4-hydroxylase domain (PHD) oxygen sensor proteins

Cellular oxygen is sensed by prolyl-4-hydroxylase domain (PHD) proteins that hydroxylate hypoxia-inducible factor (HIF) alpha subunits. Under normoxic conditions, hydroxylated HIFalpha is bound by the von Hippel-Lindau (pVHL) tumor suppressor, leading to ubiquitinylation and proteasomal degradation. Under hypoxic conditions, hydroxylation becomes reduced, leading to HIFalpha stabilization. The authors recently showed that changes in PHD abundance and activity can regulate HIFalpha stability under normoxic as well as under hypoxic conditions. Thus, the PHD oxygen sensors themselves represent effectors of cellular signalling pathways as well as potential drug targets. Here, a cell-free in vitro microtiter plate-based peptide hydroxylation assay was used to investigate the influence of ferrous iron, Krebs cycle intermediates, transition metals, and vitamin C and other antioxidants on the activity of purified PHD1 to 3. PHD activity depends not only on oxygen availability but is also regulated by iron, vitamin C, and Krebs cycle intermediates, suggesting a physiological relevance of their cellular concentrations. Copper but not iron, cobalt, or nickel salts catalyzed vitamin C oxidation. While vitamin C is essential for PHD activity in vitro, N-acetyl-L-cysteine had no effect, and gallic acid or n-propyl gallate efficiently inhibited the activity of all three PHDs, demonstrating different functions of these antioxidants.

Male germ cell expression of the PAS domain kinase PASKIN and its novel target eukaryotic translation elongation factor eEF1A1

PASKIN links energy flux and protein synthesis in yeast, regulates glycogen synthesis in mammals, and has been implicated in glucose-stimulated insulin production in pancreatic beta-cells. Using newly generated monoclonal antibodies, PASKIN was localized in the nuclei of human testis germ cells and in the midpiece of human sperm tails. A speckle-like nuclear pattern was observed for endogenous PASKIN in HeLa cells in addition to its cytoplasmic localization. By yeast two-hybrid screening, we identified the multifunctional eukaryotic translation elongation factor eEF1A1 as a novel interaction partner of PASKIN. This interaction was mapped to the PAS A and kinase domains of PASKIN and to the C-terminus of eEF1A1 using mammalian two-hybrid and GST pull-down assays. Kinase assays, mass spectrometry and site-directed mutagenesis revealed PASKIN auto-phosphorylation as well as eEF1A1 target phosphorylation mainly but not exclusively at Thr432. Wild-type but not kinase-inactive PASKIN increased the in vitro translation of a reporter cRNA. Whereas eEF1A1 did not localize to the nucleus, it co-localizes with PASKIN to the cytoplasm of HeLa cells. The two proteins also showed a remarkably similar localization in the midpiece of the sperm tail. These data suggest regulation of eEF1A1 by PASKIN-dependent phosphorylation in somatic as well as in sperm cells.

Glucose-stimulated insulin production in mice deficient for the PAS kinase PASKIN

The Per-ARNT-Sim (PAS) domain serine/threonine kinase PASKIN, or PAS kinase, links energy flux and protein synthesis in yeast and regulates glycogen synthase in mammals. A recent report suggested that PASKIN mRNA, protein, and kinase activity are increased in pancreatic islet beta-cells under hyperglycemic conditions and that PASKIN is necessary for insulin gene expression. We previously generated Paskin knockout mice by targeted replacement of the kinase domain with the beta-geo fusion gene encoding beta-galactosidase reporter activity. Here we show that no 5-bromo-4-chloro-3-indolyl-ss-d-galactopyranoside (X-gal) staining was observed in islet beta-cells derived from Paskin knockout mice, irrespective of the ambient glucose concentration, whereas adenoviral expression of the lacZ gene in beta-cells showed strong X-gal staining. No induction of PASKIN mRNA could be detected in insulinoma cell lines or in islet beta-cells. Increasing glucose concentrations resulted in PASKIN-independent induction of insulin mRNA levels and insulin release. PASKIN mRNA levels were high in testes but undetectable in pancreas and in islet beta-cells. Finally, blood glucose levels and glucose tolerance after intraperitoneal glucose injection were indistinguishable between Paskin wild-type and knockout mice. These results suggest that Paskin gene expression is not induced by glucose in pancreatic beta-cells and that glucose-stimulated insulin production is independent of PASKIN.

Increased prolyl 4-hydroxylase domain proteins compensate for decreased oxygen levels. Evidence for an autoregulatory oxygen-sensing system

Prolyl 4-hydroxylase domain (PHD) proteins are oxygen-dependent enzymes that hydroxylate hypoxia-inducible transcription factor (HIF) alpha-subunits, leading to their subsequent ubiquitination and degradation. Paradoxically, the expression of two family members (PHD2 and PHD3) is induced in hypoxic cell culture despite the reduced availability of the oxygen co-substrate, and it has been suggested that they become functionally relevant following re-oxygenation to rapidly terminate the HIF response. Here we show that PHDs are also induced in hypoxic mice in vivo, albeit in a tissue-specific manner. As demonstrated under chronically hypoxic conditions in vitro, PHD2 and PHD3 show a transient maximum but remain up-regulated over more than 10 days, suggesting a feedback down-regulation of HIF-1alpha which then levels off at a novel set point. Indeed, hypoxic induction of PHD2 and PHD3 is paralleled by the attenuation of endogenous HIF-1alpha. Using an engineered oxygen-sensitive reporter gene in a cellular background lacking endogenous HIF-1alpha and hence inducible PHD expression, we could show that increased exogenous PHD levels can compensate for a wide range of hypoxic conditions. Similar data were obtained in a reconstituted cell-free system in vitro. In summary, these results suggest that due to their high O2 Km values, PHDs have optimal oxygen-sensing properties under all physiologically relevant oxygen concentrations; increased PHDs play a functional role even under oxygen-deprived conditions, allowing the HIF system to adapt to a novel oxygen threshold and to respond to another hypoxic insult. Furthermore, such an autoregulatory oxygen-sensing system would explain how a single mechanism works in a wide variety of differently oxygenated tissues.

Surgical management of retraction pockets of the pars tensa with cartilage and perichondrial grafts

Stable, self-cleansing retraction pockets of the pars tensa are common incidental findings and require no treatment. In other cases, recurrent discharge occurs and there may also be associated conductive hearing loss. In a minority of cases, cholesteatoma may develop.

This paper presents the results of surgery using a graft composed of cartilage and perichondrium for retraction pockets involving the posterior half of the tympanic membrane, as well as early results using a larger graft designed to manage retraction of the entire tympanic membrane. Data on 51 patients with posterior retraction pockets are presented. Forty-two (82 per cent) patients had no aural discharge one year following surgery and the tympanic membrane was not retracted in 43 (84 per cent). The larger ‘Mercedes-Benz’ graft was used in four patients and the results obtained suggested that it may prove a successful technique for extensive retraction pockets.

Oxygen-regulated expression of TGF-beta 3, a growth factor involved in trophoblast differentiation

The transforming growth factor-beta 3 (TGF-beta 3) is involved in oxygen-dependent differentiation processes during placental development and pregnancy disorders. However, the importance of oxygen partial pressure for the regulation of TGF-beta 3 expression is presently unclear. We and others presented preliminary evidence that the hypoxia-inducible factor-1 (HIF-1) confers TGF-beta 3 transcription but it was unknown whether this occurred directly or indirectly. To analyze how HIF-1 regulates TGF-beta 3 gene transcription, we cloned and sequenced the mouse TGF-beta 3 promoter region. Multiple putative HIF-1 binding sites (HBSs) were identified, many of which co-localized with two G+C rich CpG islands 5' to the TGF-beta 3 transcription start site. A 6.8 kb fragment of the TGF-beta 3 promoter induced reporter gene expression under hypoxic conditions or when treated with an iron chelator known to stabilize and activate the HIF-1 alpha subunit. Deletion of a 2.4 kb fragment upstream of the distal CpG island abolished inducibility of reporter gene expression. Two HBSs (HBS1 and HBS6) that bound the HIF-1 protein could be identified within this 2.4 kb fragment. These results suggest that TGF-beta 3 gene expression is directly regulated by HIF-1.

Simultaneous exposure of rats to dioxin and carbon monoxide reduces the xenobiotic but not the hypoxic response

Aryl hydrocarbon receptor (AhR) and hypoxiainducible factor-1α (HIF-1α) are conditionally regulated transcription factor subunits that form heterodimeric complexes with their common partner, AhR nuclear translocator (ARNT/HIF-1β). Whereas the environmentally toxic compound 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD) initiates the trans-activation activity of AhR:ARNT/HIF-1β, hypoxic exposure stabilizes HIF-1α and functionally activates the HIF-1α:ARNT/HIF-1β complex. To analyze a possible crosstalk between these two pathwaysin vivo, rats were given dioxin orally and/or were exposed to carbon monoxide (CO), causing functional anemia. We found that exposure to CO inhibited the xenobiotic response while dioxin application had no significant negative impact on hypoxia-mediated gene transcription.

Mammalian PASKIN, a PAS-serine/threonine kinase related to bacterial oxygen sensors

The PAS domain is a versatile protein fold found in many archaeal, bacterial, and plant proteins capable of sensing environmental changes in light intensity, oxygen concentration, and redox potentials. The oxygen sensor FixL from Rhizobium species contains a heme-bearing PAS domain and a histidine kinase domain that couples sensing to signaling. We identified a novel mammalian PAS protein (PASKIN) containing a domain architecture resembling FixL. PASKIN is encoded by an evolutionarily conserved single-copy gene which is ubiquitously expressed. The human PASKIN and mouse Paskin genes show a conserved intron-exon structure and share their promoter regions with another ubiquitously expressed gene that encodes a regulator of protein phosphatase-1. The 144-kDa PASKIN protein contains a PAS region homologous to the FixL PAS domain and a serine/threonine kinase domain which might be involved in signaling. Thus, PASKIN is likely to function as a mammalian PAS sensor protein.

Dominant suppressor mutation bypasses the sphingolipid requirement for growth of Saccharomyces cells at low pH: role of the CWP2 gene

Strains of Saccharomyces cerevisiae termed sphingolipid compensatory (SLC) do not grow at low pH when the cells lack sphingolipids. To begin to understand why sphingolipids are required for growth at low pH, we isolated derivatives of SLC strains, termed low pH resistant (LprR), carrying the LPR suppressor gene that allows growth at pH 4.1 when cells lack sphingolipids. Suppression is due to mutation of a single nuclear gene. The LPR suppressor gene functions, at least in part, by enhancing the ability of cells lacking sphingolipids to generate a net efflux of protons in suspension fluid with a pH range of 4.0-6.0. The LPR suppressor gene also enables cells lacking sphingolipids to maintain their intracellular pH near neutrality when the pH of the suspension fluid is low, unlike cells lacking the suppressor gene, which cannot maintain their intracellular pH in the face of a low external pH. These results demonstrate that some functions(s) of sphingolipids necessary for growth at low pH can be bypassed by a suppressor mutation. Attempts to clone the LPR suppressor gene were not successful, but they led to the isolation of the CWP2 gene, which encodes a major mannoprotein component of the outer cell wall. It was isolated because an increased copy number has the unusual property of increasing the frequency at which LprR strains arise. As we show here, part of the reason for this effect is that the CWP2 gene is essential for generating a net efflux of protons and for controlling intracellular pH in LprR strains that lack sphingolipids. These results suggest new cellular functions for the Cwp2 protein.

Epolones induce erythropoietin expression via hypoxia-inducible factor-1 alpha activation

Induction of erythropoietin (Epo) expression under hypoxic conditions is mediated by the heterodimeric hypoxia-inducible factor (HIF)-1. Following binding to the 3' hypoxia-response element (HRE) of the Epo gene, HIF-1 markedly enhances Epo transcription. To facilitate the search for HIF-1 (ant)agonists, a hypoxia-reporter cell line (termed HRCHO5) was constructed containing a stably integrated luciferase gene under the control of triplicated heterologous HREs. Among various agents tested, we identified a class of substances called epolones, which induced HRE-dependent reporter gene activity in HRCHO5 cells. Epolones are fungal products known to induce Epo expression in hepatoma cells. We found that epolones (optimal concentration 4-8 micromol/L) potently induce HIF-1 alpha protein accumulation and nuclear translocation as well as HIF-1 DNA binding and reporter gene transactivation. Interestingly, the activity of a compound related to the fungal epolones, ciclopirox olamine (CPX), was blocked after addition of ferrous iron. This suggests that CPX might interfere with the putative heme oxygen sensor, as has been proposed for the iron chelator deferoxamine mesylate (DFX). However, about 10-fold higher concentrations of DFX (50-100 micromol/L) than CPX were required to maximally induce reporter gene activity in HRCHO5 cells. Moreover, structural, functional, and spectrophotometric data imply a chelator:iron stoichiometry of 1:1 for DFX but 3:1 for CPX. Because the iron concentration in the cell culture medium was determined to be 16 micromol/L, DFX but not CPX function can be explained by complete chelation of medium iron. These results suggest that the lipophilic epolones might induce HIF-1 alpha by intracellular iron chelation. (Blood. 2000;96:1558-1565)

General applicability of chicken egg yolk antibodies: the performance of IgY immunoglobulins raised against the hypoxia-inducible factor 1alpha

Avian embryos and neonates acquire passive immunity by transferring maternal immunoglobulins from serum to egg yolk. Despite being a convenient source of antibodies, egg yolk immunoglobulins (IgY) from immunized hens have so far received scant attention in research. Here we report the generation and rapid isolation of IgY from the egg yolk of hens immunized against the alpha subunit of the human hypoxia-inducible factor 1 (HIF-1alpha). Anti-HIF-1alpha IgY antibodies were affinity purified and tested for their performance in various applications. Abundant HIF-1alpha protein was detected by Western blot analysis in nuclear extracts derived from hypoxic cells of human, mouse, monkey, swine, and dog origin whereas in hypoxic quail and frog cells, the HIF-1alpha signal was weak or absent, respectively. In electrophoretic mobility shift assays, affinity-purified IgY antibody was shown to recognize the native HIF-1 (but not the related HIF-2) complex that specifically binds an oligonucleotide containing the HIF-1 DNA binding site. Furthermore, IgY antibody immunoprecipitated HIF-1alpha from hypoxic cell extracts. Immunofluorescence experiments using IgY antibody allowed the detection of HIF-1alpha in the nucleus of hypoxic COS-7 cells. For comparison, the application of a mouse monoclonal antibody raised against the identical HIF-1alpha fragment was more restricted. Because chicken housing is inexpensive, egg collection is noninvasive, isolation and affinity purification of IgY antibodies are fast and simple, and the applicability of IgY is widespread, immunization of hens represents an excellent alternative for the generation of polyclonal antibodies.

Mouse hypoxia-inducible factor-1alpha is encoded by two different mRNA isoforms: expression from a tissue-specific and a housekeeping-type promoter

Hypoxic induction of erythropoietin (Epo) and other oxygen-dependent genes is mediated by the hypoxia-inducible factor-1 (HIF-1), a heterodimeric transactivator consisting of an alpha and a beta subunit. We previously found that the mouse gene encoding HIF-1alpha harbors two alternative first exons (I.1 and I.2), giving rise to two different HIF-1alpha mRNA isoforms. Here, we show by RNase protection analysis that the exon I.1-derived mRNA isoform is differentially expressed in mouse tissues, being highest in kidney, tongue, stomach, and testis, but undetectable in liver, whereas the exon I.2 mRNA isoform is ubiquitously expressed. Sequence and methylation analysis showed that, in contrast to exon I.1, exon I.2 resides within a region showing typical features of a CpG island, known to be associated with the 5' end of housekeeping genes. We identified a 232-bp minimal exon I.2 promoter that strongly induced reporter gene expression in mouse L929 fibroblasts and Hepa1 hepatoma cells. In contrast to L929 cells, the exon I.1 promoter was inactive in Hepa1 cells and hypoxic exposure (1% O2) markedly reduced exon I.2 promoter activity in Hepa1 cells. Prolonged exposure of mice to hypoxia (7.5% O2 for up to 72 hours) also caused a decrease in liver HIF-1alpha mRNA, whereas aldolase mRNA levels increased. These findings might be related to the relatively low Epo levels in the adult liver.

The mouse gene for hypoxia-inducible factor-1alpha--genomic organization, expression and characterization of an alternative first exon and 5' flanking sequence

The ubiquitously expressed hypoxia-inducible factor-1 (HIF-1) is involved in expression of a large number of oxygen-regulated genes. HIF-1 is a heterodimer consisting of an alpha and a beta subunit, both belonging to the basic-helix-loop-helix Per-aryl hydrocarbon receptor nuclear translocator-Sim (PAS) family of transcription factors. Whereas HIF-1alpha is a novel member of this family, HIF-1beta is identical to the aryl hydrocarbon receptor nuclear translocator, previously recognized to be involved in xenobiotic metabolism. cDNA cloning revealed that mouse HIF-1alpha can be expressed as two mRNA isoforms containing alternative 5' untranslated regions and two different predicted translational start sites. We cloned and characterized 20.5 kb of the mouse HIF-1alpha gene (Hif1a) containing exon II-XV. The two alternative first exons, I.1 and I.2, are separated from exon II by approximately 24 kb and 17 kb, respectively. We also sequenced Hif1a exon I.1 and flanking regions, and mapped a single exon I.1 transcription initiation site. Reverse transcription PCR analysis of total RNA derived from normoxic and hypoxic mouse hepatoma and fibroblast cell lines suggested that the two alternative mRNA isoforms are constitutively coexpressed in these cells, and that two different promoters drive transcription of HIF-1alpha. A minimal exon I.1 promoter was identified which moderately activated heterologous gene expression, indicating that additional cis-elements are required for efficient HIF-1alpha transcription in vivo.

Molecular genetics of aristaless, a prd-type homeo box gene involved in the morphogenesis of proximal and distal pattern elements in a subset of appendages in Drosophila

Viable aristaless (al) mutations of Drosophila affect pattern elements at both ends of the proximodistal axis in a subset of adult appendages. The al gene has been cloned and identified by P-element-mediated germ-line transformation with a genomic DNA fragment, which rescues a lethal mutation of al as well as aspects of the adult al phenotype. The al gene contains a prd-type homeo domain and a Pro/Gln-rich domain and, hence, probably encodes a transcription factor. Its transcript distribution in third-instar imaginal discs closely corresponds to the anlagen of the tissues that later become visibly affected in adult al mutants. The striking similarity of a bimodal al expression in different imaginal discs indicates that al is under the control of a "prepattern," which is shared at least among antennal, leg, and wing discs. The al gene is also transcribed during embryogenesis. Apart from a function in the ontogeny of specific larval head and tail organs, its embryonic transcript pattern suggests a possible role in early imaginal disc development.

The paired box gene pox neuro: A determiant of poly-innervated sense organs in Drosophila

This study describes the structure and function of pox neuro (poxn), a gene previously isolated by virtue of a conserved domain, the paired box, which it shares with the segmentation genes paired and gooseberry. Its expression pattern has been analyzed, particularly during development of the PNS. We propose that poxn is a "neuroblast identity" gene acting in both the PNS and the CNS on the basis of the following evidence. Its expression is restricted to four neuronal precursors in each hemisegment: two neuronal stem cells (neuroblasts) in the CNS, and two sensory mother cells (SMCs) in the PNS. The SMCs that express poxn produce the poly-innervated external sense organs of the larva. In poxn- embryos, poly-innervated sense organs are transformed into mono-innervated. Conversely, ectopic expression of poxn in embryos transformed with a heat-inducible poxn gene can switch mono-innervated to poly-innervated sense organs. Expression of poxn in the wing disc is restricted to the SMCs of the poly-innervated sense organs, suggesting that poxn also determines the lineage of poly-innervated adult sense organs.

Removal of psoralen monoadducts and crosslinks by human cell free extracts

Human cell free extracts are capable of carrying out damage-induced DNA synthesis in response to DNA damage by UV, psoralen, and cisplatin. We show that this damage-induced DNA synthesis is associated with removal of psoralen adducts and therefore is 'repair synthesis' and not an aberrant DNA synthesis reaction potentiated by DNA deformed by adducts. By comparing the denaturable fraction of psoralen adducted DNA which becomes labeled in the repair reaction to that of terminally labeled DNA (without repair) we have found that all DNA synthesis induced by psoralen monoadducts is the consequence of removal of these adducts. By the same approach we have obtained preliminary evidence that this in vitro system is capable of removing psoralen crosslinks as well.

[Preliminary results concerning the value of chemotherapy in the treatment of inoperable bronchial carcinoma (excluding small-cell anaplastic carcinoma)]

Inoperable non- microcellular primary bronchial carcinomas have been reputed up to now to be chemo-resistant. The introduction of Cis-platinum into a polychemotherapy protocol leads to revision of this concept. The authors report the preliminary results of a polychemotherapy protocol (including Cis-platinum, Vindesine, CCNU, Cyclophosphamide) associated, in cases of non- metastasized carcinomas, with radiotherapy to the tumour itself, the mediastinum and the supraclavicular fossae. These results confirmed the value of such chemotherapy in forms with metastases. In localised inoperable forms, conclusions could be reached only on the basis of a randomised comparative trial of chemotherapy + radiotherapy versus radiotherapy alone.