Differential regulation of glial cell line‐derived neurotrophic factor (GDNF) mRNA expression during hypoxia and reoxygenation in astrocytes isolated from stroke‐prone spontaneously hypertensive rats

Abstract

Glial cell line-derived neurotrophic factor (GDNF) plays several important roles in the survival and recovery of mature neurons during ischemia. We examined the possibility that the expression of GDNF mRNA and the release of GDNF protein are regulated differentially in cultured astrocytes from the stroke-prone spontaneously hypertensive rat (SHRSP) compared with those from Wistar Kyoto rats (WKY) during hypoxia and reoxygenation (H/R) and after exposure to glutamate and hydrogen peroxide (H(2)O(2)). The mRNA expression was quantitated by reverse transcription-polymerase chain reaction (RT-PCR) based on the fluorescent TaqMan methodology. A new instrument capable of measuring fluorescence in real-time was used to quantify gene amplification in astrocytes. GDNF protein was investigated by enzyme-linked immunosorbent assay (ELISA). GDNF mRNA expression and GDNF protein release at normoxia were greater in SHRSP than in WKY astrocytes. During H/R, however, the mRNA expression and protein release tended to be reduced in SHRSP compared with WKY. Glutamate and H(2)O(2) induced the expression of GDNF mRNA and the release of GDNF protein in both WKY and SHRSP in a dose-dependent manner. Levels of GDNF mRNA and protein in SHRSP were significantly lower than in WKY. These findings indicate that GDNF production in SHRSP astrocytes was low in response to H/R, glutamate, and H(2)O(2), compared with that observed in WKY. We conclude that the attenuated production of GDNF in astrocytes is involved in neuronal vulnerability in SHRSP during H/R, as GDNF production, which is stimulated by glutamate and H(2)O(2), is closely related to the protective effect against H/R-mediated neurotoxicity.

Driving GDNF expression: The green and the red traffic lights

“…Sub-seizure doses of the glutamate receptor agonists N-methyl-D-aspartate (NMDA) or kainate increase GDNF mRNA levels in the adult rat striatum, and similar findings come from striatal astrocyte cultures (Ho et al, 1995). Moreover, glutamate induces the expression of GDNF mRNA and the release of GDNF protein in a concentration-dependent manner in cultured rat astrocytes (Yamagata et al, 2002). Altogether, these results indicate that activation of glutamate receptors is able to modulate GDNF expression and suggest a role for GDNF in neuronal plasticity.…”

“…Transcription factors 9.5.1. Role of NF-kB H 2 O 2 increases GDNF mRNA levels in rat astrocytes (Yamagata et al, 2002;Koyama et al, 2003a) and induces GDNF release (Verity et al, 1998;Yamagata et al, 2002). H 2 O 2 also up-regulates GDNF mRNA and protein levels in substantia nigra neuron-glia cell cultures thereby protecting dopaminergic neurons from H 2 O 2 -induced toxicity (Saavedra et al, 2006).…”

Multiple receptor tyrosine kinases regulate HIF-1α and HIF-2α in normoxia and hypoxia in neuroblastoma: implications for antiangiogenic mechanisms of multikinase inhibitors

“…To our knowledge, this is the first study demonstrating that HIF-1a levels are regulated by RET and PDGFR-b. Transcription of the RET ligand, GDNF, is thought to be hypoxiaregulated, possibly through HIF-1a (Yamagata et al, 2002), and the expression of ligands for PDGFR-b, EGFR and VEGFR is HIF-1a controlled, suggesting the presence of a feed-forward loop (Semenza, 2003;Yoshida et al, 2006). Indeed, the observation that multiple RTKs regulate HIF may represent a normal, It is noteworthy that VEGFR-1, but not other RTKs, induced rises in HIF-a In light of the finding that VEGFR-1 activation on pancreatic cancer cells mediates epithelial-mesenchymal transition , and our finding that HIF-2a overexpression promotes an epithelial-mesenchymal transition phenotype (Kim et al, 2009), it suggests a role for the VEGFR-1/HIF-2a pathway in tumor cell invasiveness and mesenchymal phenotype.…”

Interplay between receptor tyrosine kinases and hypoxia signaling in cancer

“…The crosstalk between RET and HIF-1α has been described also in neuroblastoma cells, where activation of RET induced by its ligand GDNF increases HIF-1α protein levels [130]. In turn, expression of GDNF was reported to be increased in hypoxic rat astrocytes [168]. This ligand-dependent stimulation may create a positive feedback loop in the hypoxic pathway.…”

“…Increased expression potentially mediated by HIF-1α [130,168] Non-small cell lung cancer (NSCLC), RCC, breast cancer, prostate cancer, glioblastoma cells EGFR mRNA translation through activated HIF-2α [76,79] 786-0 ccRCC cells EGFR Delayed receptor endocytosis [81] 786-O ccRCC EGFR Ligand-independent activation through elevated expression of CAV1 [86] T-47D and MDA-MB-468 breast cancer cells, HEK293 human embryonic kidney cells…”