NFAT5 and HIF-1α Coordinate to Regulate NKCC1 Expression in Hippocampal Neurons After Hypoxia-Ischemia

Abstract

Hypoxic-ischemic encephalopathy (HIE) is a serious birth complication with severe long-term sequelae such as cerebral palsy, epilepsy and cognitive disabilities. Na + -K + -2Cl − cotransporters 1 (NKCC1) is dramatically upregulated after hypoxia-ischemia (HI), which aggravates brain edema and brain damage. Clinically, an NKCC1-specific inhibitor, bumetanide, is used to treat diseases related to aberrant NKCC1 expression, but the underlying mechanism of aberrant NKCC1 expression has rarely been studied in HIE. In this study, the cooperative effect of hypoxia-inducible factor-1α (HIF-1α) and nuclear factor of activated T cells 5 (NFAT5) on NKCC1 expression was explored in hippocampal neurons under hypoxic conditions. HI increased HIF-1α nuclear localization and transcriptional activity, and pharmacological inhibition of the HIF-1α transcription activity or mutation of hypoxia responsive element (HRE) motifs recovered the hypoxiainduced aberrant expression and promoter activity of NKCC1. In contrast, oxygenglucose deprivation (OGD)-induced downregulation of NFAT5 expression was reversed by treating with hypertonic saline, which ameliorated aberrant NKCC1 expression. More importantly, knocking down NFAT5 or mutation of the tonicity enhancer element (TonE) stimulated NKCC1 expression and promoter activity under normal physiological conditions. The positive regulation of NKCC1 by HIF-1α and the negative regulation of NKCC1 by NFAT5 may serve to maintain NKCC1 expression levels, which may shed light on the transcription regulation of NKCC1 in hippocampal neurons after hypoxia.

Hypoxia-Inducible Factor (HIF) in Ischemic Stroke and Neurodegenerative Disease

“…Under oxygen-glucose deprivation, glucose oxidation via the pentose phosphate pathway terminates oxidative stress development through modulation of redox homeostasis and the antioxidant system of the cell ( Fernandez-Fernandez et al, 2012 ; Sun et al, 2017 ; Vetrovoy et al, 2019 ). During hypoxia, HIF-1 also strongly upregulates expression of the gene encoding the Na + -dependent chloride transporter NKCC1 ( Yang et al, 2019 ). In recent studies in rat models of stroke and TBI, NKCC1 expressed in brain endothelial cells appears to be a critical mediator of edema formation and/or progressive secondary hemorrhage ( Simard et al, 2010 ).…”

Long Noncoding RNA X-Inactive-Specific Transcript Promotes the Secretion of Inflammatory Cytokines in LPS Stimulated Astrocyte Cell Via Sponging miR-29c-3p and Regulating Nuclear Factor of Activated T cell 5 Expression

“…Increased NFAT5 expression induced by inflammatory signals aggravated bloodbrain barrier injury, neuroinflammation, and neuron hyperexcitability-induced epilepsy (42). In contrast, NFAT5 overexpression protected the astrocytes against ischemic damages and inhibited neuron hyperexcitability-induced seizures (43). In this study, NFAT5 expression was increased in LPS-stimulated CTX- , TNF-a, and L-glutamate levels were assessed using an assay kit according to the standard procedures after transfection in LPS-treated CTX-TNA2 at 24 h. (F, G) Neurons cocultured with LPS-treated CTX-TNA2 (LPS group), LPS-treated CTX-TNA2 transfected si-NC (LPS+si-NC group), and LPS-treated CTX-TNA2 transfected si-NFAT5 (LPS+si-NFAT5 group), LPS-treated si-XIST-CTX-TNA2 (LPS+si-XIST group), LPS-treated si-XIST-CTX-TNA2 transfected ov-NC (LPS+si-XIST+ov-NC group), and LPS-treated si-XIST-CTX-TNA2 transfected ov-NFAT5 (LPS+si-XIST+ ov-NFAT5 group), respectively.…”

Increased intracellular Cl− concentration in pulmonary arterial myocytes is associated with chronic hypoxic pulmonary hypertension

“…The hypoxia-inducible factor-1 (HIF-1), that is expressed under hypoxic condition, upregulates the transcription of Slc12a2/NKCC1 in hippocampal neurons (39), but decreases NKCC1 expression in intestinal epithelial cells (40). There is currently no report about the influence of hypoxia or HIF-1 on the expression and function of NKCC1 in VSMCs.…”