Up-regulation of the manganese transporter SLC30A10 by hypoxia-inducible factors defines a homeostatic response to manganese toxicity

Manganese (Mn) is an essential metal that induces incurable parkinsonism at elevated levels. However, unlike other essential metals, mechanisms that regulate mammalian Mn homeostasis are poorly understood, which has limited therapeutic development. Here, we discovered that the exposure of mice to a translationally relevant oral Mn regimen up-regulated expression of SLC30A10, a critical Mn efflux transporter, in the liver and intestines. Mechanistic studies in cell culture, including primary human hepatocytes, revealed that 1) elevated Mn transcriptionally up-regulated SLC30A10, 2) a hypoxia response element in the SLC30A10 promoter was necessary, 3) the transcriptional activities of hypoxia-inducible factor (HIF) 1 or HIF2 were required and sufficient for the SLC30A10 response, 4) elevated Mn activated HIF1/HIF2 by blocking the prolyl hydroxylation of HIF proteins necessary for their degradation, and 5) blocking the Mn-induced up-regulation of SLC30A10 increased intracellular Mn levels and enhanced Mn toxicity. Finally, prolyl hydroxylase inhibitors that stabilize HIF proteins and are in advanced clinical trials for other diseases reduced intracellular Mn levels and afforded cellular protection against Mn toxicity and also ameliorated the in vivo Mn-induced neuromotor deficits in mice. These findings define a fundamental homeostatic protective response to Mn toxicity—elevated Mn levels activate HIF1 and HIF2 to up-regulate SLC30A10, which in turn reduces cellular and organismal Mn levels, and further indicate that it may be possible to repurpose prolyl hydroxylase inhibitors for the management of Mn neurotoxicity.

AAV2-mediated and hypoxia response element-directed expression of bFGF in neural stem cells showed therapeutic effects on spinal cord injury in rats

Neural stem cell (NSCs) transplantation has been one of the hot topics in the repair of spinal cord injury (SCI). Fibroblast growth factor (FGF) is considered a promising nerve injury therapy after SCI. However, owing to a hostile hypoxia condition in SCI, there remains a challenging issue in implementing these tactics to repair SCI. In this report, we used adeno-associated virus 2 (AAV2), a prototype AAV used in clinical trials for human neuron disorders, basic FGF (bFGF) gene under the regulation of hypoxia response element (HRE) was constructed and transduced into NSCs to yield AAV2-5HRE-bFGF-NSCs. Our results showed that its treatment yielded temporally increased expression of bFGF in SCI, and improved scores of functional recovery after SCI compared to vehicle control (AAV2-5HRE-NSCs) based on the analyses of the inclined plane test, Basso–Beattie–Bresnahan (BBB) scale and footprint analysis. Mechanistic studies showed that AAV2-5HRE-bFGF-NSCs treatment increased the expression of neuron-specific neuronal nuclei protein (NeuN), neuromodulin GAP43, and neurofilament protein NF200 while decreased the expression of glial fibrillary acidic protein (GFAP) as compared to the control group. Further, the expressions of autophagy-associated proteins LC3-II and Beclin 1 were decreased, whereas the expression of P62 protein was increased in AAV2-5HRE-bFGF-NSCs treatment group. Taken together, our data indicate that AAV2-5HRE-bFGF-NSCs treatment improved the recovery of SCI rats, which is accompanied by evidence of nerve regeneration, and inhibition of SCI-induced glial scar formation and cell autophagy. Thus, this study represents a step forward towards the potential use of AAV2-5HRE-bFGF-NSCs for future clinical trials of SCI repair.

Short tandem repeat near hypoxia response element (HRE) instead of HRE genetic variants in promoter calcitonin receptor-like receptor (CRLR) gene as risk factor in severe preeclampsia: a preliminary study

Objective Calcitonin receptor-like receptor (CRLR) regulates vasoconstriction and dilatation; the expression increases during hypoxia via activation of hypoxia response element (HRE) in CRLR gene promoter region. Variant in HRE, as well short tandem repeat (STR) variants near HRE in CRLR alters the gene expression. This study focused on a case–control study to investigate the expression of genetic typing CLRL promoter variant in pregnant women with severe preeclampsia and normal pregnancies, we also tried to describe interesting findings of the genetic expression in anemic patients in the severe preeclampsia group. Our aimed to observe the correlation of CRLR gene promoter variant and anemia in severe preeclampsia. Results There was no nucleotide variant in HRE; CACA box prior to HRE varied in length (15–24); CACA box with length > 20 was used as cut off point. Hb was lower in CACA box length ≥ 21 (10.33 ± 1.57) vs. < 21 (11.01 ± 1.67; p = 0.391). CACA box polymorphism and anemia were correlated in severe preeclampsia (p = 0.005) OR 0.038 (CI 0.003–0.544); not in normal (p = 0.069).

Zebrafish Hif3α modulates erythropoiesis via regulation of gata1 to facilitate hypoxia tolerance

ABSTRACTThe hypoxia-inducible factors 1α and 2α (HIF1α and HIF2α) are master regulators of the cellular response to O2. In addition to HIF1α and HIF2α, HIF3α is another identified member of the HIFα family. Even though the question of whether some HIF3α isoforms have transcriptional activity or repressive activity is still under debate, it is evident that the full length of HIF3α acts as a transcription factor. However, its function in hypoxia signaling is largely unknown. Here, we show that loss of hif3a in zebrafish reduced hypoxia tolerance. Further assays indicated that erythrocyte number was decreased because red blood cell maturation was impeded by hif3a disruption. We found that gata1 expression was downregulated in hif3a null zebrafish, as were several hematopoietic marker genes, including alas2, band3, hbae1, hbae3 and hbbe1. Hif3α recognized the hypoxia response element located in the promoter of gata1 and directly bound to the promoter to transactivate gata1 expression. Our results suggested that hif3a facilities hypoxia tolerance by modulating erythropoiesis via gata1 regulation.

ILKAP Binding to and Dephosphorylating HIF-1α is Essential for Apoptosis Induced by Severe Hypoxia

Background/Aims: Integrin-linked kinase-associated phosphatase (ILKAP), a serine/threonine phosphatase that belongs to the protein phosphatase 2C family, has a role in cell survival and apoptosis. Hypoxia-inducible factor 1α (HIF-1α) is the key transcription factor in the response to oxygen deficiency in mammals. Direct phosphorylation and dephosphorylation of HIF-1α affect its function. The present study investigated the role of ILKAP on HIF-1α dephosphorylation and cell behavior. Methods: HIF-1α was induced by hypoxia. Physical binding between ILKAP and HIF-1α was demonstrated by a co-immunoprecipitation assay. HIF-1α transcriptional activity was investigated using a hypoxia-response element-containing luciferase reporter plasmid. Cell viability was evaluated by a trypan blue dye exclusion assay. ILKAP function was explored by a gain and loss assay with an overexpression plasmid and shRNA infection. Results: ILKAP physically interacted with HIF-1α and induced its dephosphorylation. Both the HIF-1α-p53 interaction and apoptosis relied on ILKAP. Conclusion: The results indicated that the ILKAP directly binds and dephosphorylates HIF-1α and responsible for severe hypoxia-induced cell apoptosis.