Intermittent hypoxia-induced protein phosphatase 2A activation reduces PC12 cell proliferation and differentiation

Abstract

BackgroundIntermittent hypoxia (IH) plays a critical role in sleep breathing disorder-associated hippocampus impairments, including neurocognitive deficits, irreversible memory and learning impairments. IH-induced neuronal injury in the hippocampus may result from reduced precursor cell proliferation and the relative numbers of postmitotic differentiated neurons. However, the mechanisms underlying IH-induced reactive oxygen species (ROS) generation effects on cell proliferation and neuronal differentiation remain largely unknown.ResultsROS generation significantly increased after 1–4 days of IH without increased pheochromocytoma-12 (PC12) cell death, which resulted in increased protein phosphatase 2A (PP2A) mRNA and protein levels. After 3–4 days of IH, extracellular signal-regulated kinases 1/2 (ERK1/2) protein phosphorylation decreased, which could be reversed by superoxide dismutase (SOD), 1,10-phenanthroline (Phe), the PP2A phosphorylation inhibitors, okadaic acid (OKA) and cantharidin, and the ERK phosphorylation activator nicotine (p < 0.05). In particular, the significantly reduced cell proliferation and increased proportions of cells in the G0/G1 phase after 1–4 days of IH (p < 0.05), which resulted in decreased numbers of PC12 cells, could be reversed by treatment with SOD, Phe, PP2A inhibitors and an ERK activator. In addition, the numbers of nerve growth factor (NGF)-induced PC12 cells with neurite outgrowths after 3–4 days of IH were less than those after 4 days of RA, which was also reversed by SOD, Phe, PP2A inhibitors and an ERK activator.ConclusionsOur results suggest that IH-induced ROS generation increases PP2A activation and subsequently downregulates ERK1/2 activation, which results in inhibition of PC12 cell proliferation through G0/G1 phase arrest and NGF-induced neuronal differentiation.

Melatonin attenuates apoptosis and mitochondrial depolarization levels in hypoxic conditions of SH-SY5Y neuronal cells induced by cobalt chloride (CoCl2)

“…Liu et al (2009) reported that hypoxia-induced apoptosis is related to p38MAPK activity in cultured rat cerebellar neurons. However, MAPK members can be activated by ROS products generated intracellularly, as well as by an exterior substance, such as H 2 O 2 administered (Banno et al, 2001;Gaitanaki et al, 2007;Chen et al, 2009Chen et al, , 2014. Our findings are consistent with those of the previous studies mentioned above and comparable with the recent evidence that the members of different proteins such as ERK1/2, p38MAPK, and MAPKs mediate neuronal apoptosis.…”

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Altered Wnt Signaling Pathway in Cognitive Impairment Caused by Chronic Intermittent Hypoxia

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