Protein Kinase CK2 Increases Glutamatergic Input in the Hypothalamus and Sympathetic Vasomotor Tone in Hypertension

Abstract

Increased glutamatergic input in the paraventricular nucleus (PVN) is important for high sympathetic outflow in hypertension, but the associated molecular mechanisms remain unclear. Here we determined the role of protein kinase CK2 in increased N-methyl-D-aspartate receptor (NMDAR) activity in spinally projecting PVN neurons and sympathetic vasomotor tone in spontaneously hypertensive rats (SHR). The selective CK2 inhibitors 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) or 4,5,6,7-tetrabromobenzotriazole (TBB) significantly decreased the frequency of miniature excitatory postsynaptic currents (EPSCs) of labeled PVN neurons in SHR but not in Wistar-Kyoto (WKY) normotensive rats. Also, DRB abolished the inhibitory effect of the NMDAR antagonist AP5 on the frequency of mEPSCs in SHR. Treatment with DRB or TBB significantly reduced the amplitude of evoked NMDA-EPSCs but not AMPA-EPSCs in SHR. Furthermore, DRB significantly decreased the firing activity of PVN neurons in SHR but not in WKY rats. The membrane protein level of CK2α in the PVN, but not brainstem and prefrontal cortex, was significantly higher in SHR than in WKY rats. Lowering blood pressure with celiac ganglionectomy in SHR did not alter the increased CK2α level and the effects of DRB on mEPSCs and NMDA-EPSCs. In addition, intracerebroventricular injection of DRB not only significantly reduced blood pressure and lumbar sympathetic nerve discharges but also eliminated the inhibitory effect of AP5 microinjected into the PVN on sympathetic nerve activity in SHR. Our findings suggest that augmented CK2 activity critically contributes to increased pre- and postsynaptic NMDAR activity in the PVN and elevated sympathetic vasomotor tone in essential hypertension.

Casein Kinase II Inhibition Reverses Pain Hypersensitivity and Potentiated Spinal N-Methyl-d-aspartate Receptor Activity Caused by Calcineurin Inhibitor

“…NMDAR activity and phosphorylation state are dynamically controlled by a balance between the activity of protein kinases and protein phosphatases. For example, CK2 activation increases the phosphorylation and activity of NMDARs, whereas calcineurin can negatively regulate the phosphorylation and function of NMDARs in the brain (Tong et al, 1995;Lieberman and Mody, 1999;Ye et al, 2011). CK2 is an endogenous serine/threonine protein kinase widely expressed in many types of cells and is distributed in the central nervous system (Blanquet, 2000;Litchfield, 2003).…”

“…It is noteworthy that DRB is a highly specific CK2 inhibitor, and it does not affect protein kinase C, protein kinase A, calmodulin-dependent protein kinase II, or the Src tyrosine kinase (Pinna, 1990). The concentrations of DRB and TBB selected for our study have been shown to inhibit CK2 activity in rat brain slices (Lieberman and Mody, 1999;Ye et al, 2011). We recorded AMPAR-EPSCs and NMDAR-EPSCs of lamina II neurons monosynaptically evoked from dorsal root stimulation in spinal cord slices obtained from vehicletreated and FK506-treated rats.…”

Casein Kinase 2-mediated Synaptic GluN2A Up-regulation Increases N-Methyl-d-aspartate Receptor Activity and Excitability of Hypothalamic Neurons in Hypertension

“…Retrograde Labeling of PVN Presympathetic Neurons-Spinally projecting PVN neurons were labeled retrogradely as we described previously (9,10,23). Briefly, rats were anesthetized by intraperitoneal injection of a mixture of ketamine (70 mg/kg) and xylazine (6 mg/kg).…”

“…The tip of the stimulating electrode was placed on the ventral side ϳ150 m away from the neuron recorded. The neuron was held at 40 mV in the presence of the GABA A receptor antagonist bicuculline (10 M) and the non-NMDAR antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (20 M) in the aCSF (10). The sodium channel blocker lidocaine N-ethyl bromide (10 mM) was added to the pipette solution to suppress the firing activity of recorded neurons.…”

“…The glutamatergic input and excitability of PVN neurons that project to the spinal cord sympathetic preganglionic neurons are increased in SHRs (5,9). We have shown that pre-and postsynaptic N-methyl-D-aspartate receptors (NMDARs) of PVN presympathetic neurons are up-regulated and play a key role in the elevated sympathetic outflow in SHRs (5,9,10). However, the molecular mechanisms underlying increased NMDAR activity in the PVN in hypertension remain largely unknown.…”