Effects of basic fibroblast growth factor on hippocampal and parietal cortical neuronal cAMP-response element-binding protein expression in a rat model of focal cerebral ischemia/reperfusion

BACKGROUND： cAMP-response element binding protein （CREB） is a key modulator of various signaling pathways. CREB activation initiates a series of intracellular signaling pathways that promote neuronal survival. OBJECTIVE： To investigate the regulatory effects of basic fibroblast growth factor （bFGF） on cerebral neuronal CREB expression following ischemia/reperfusion injury. DESIGN, TIME AND SETTING： An immunohistochemical detection experiment was performed at the Department of Anatomy, Shenyang Medical College, between October 2006 and April 2008. MATERIALS： A total of 60 healthy, adult, Wistar rats were randomly divided into three groups： sham-operated （n =12）, ischemia/reperfusion （n = 24）, and bFGF-treated （n = 24）. Rabbit anti-rat CREB （1： 100） and biotin labeled goat anti-rabbit IgG were purchased from the Wuhan Boster Company, China. MetaMorph-evolution MP5.0-BX51 microscopy imaging system was provided by China Medical University, China. METHODS： Rat models of cerebral ischemia/reperfusion injury were developed using the suture method for right middle cerebral artery occlusion. Two-hour ischemia was followed by reperfusion. Rats from the bFGF-treated and ischemia/reperfusion groups were intraperitoneally administered endogenous bFGF （500 IU/mL, 2 000 IU/kg） or an equal amount of physiological saline. Rats from the sham-operated group underwent a similar surgical procedure, without induction of ischemia/reperfusion injury and drug administration. MAIN OUTCOME MEASURES： After 48-hour reperfusion, hippocampal and parietal cortical neuronal CREB expression was detected by immunohistochemistry, and the absorbance of hippocampal CREB-positive products was determined using MetaMorph-evolutionMP5.0-BX51 microscopy imaging system. RESULTS： The sham-operated group exhibited noticeable CREB expression in hippocampal and parietal cortical neurons. In the ischemia/reperfusion group, the CREB expression was discrete and neurons were poorly arranged. The bFGF-treated group exhibited increased CREB expression and better neuronal arrangement compared with the ischemia/reperfusion group. The mean absorbance of CREB-immunoreactive products in the hippocampus and parietal cortex was significantly higher in the ischemia/reperfusion group than in the sham-operated group （P 〈 0.05）, and significantly higher in the bFGF-treated group than in the ischemia/reperfusion group （P 〈 0.05）. CONCLUSION： bFGF significantly upregulates CREB expression in hippocampal and parietal cortical neurons following ischemia/reperfusion injury.

Changes of CREB in rat hippocampus, prefrontal cortex and nucleus accumbens during three phases of morphine induced conditioned place preference in rats

Objective: To investigate the changes in CREB (cAMP response element binding protein) in hippocampus, PFC (prefrontal cortex) and NAc (nucleus accumbens) during three phases of morphine induced CPP (conditioned place preference) in rats, and to elucidate the role of CREB during the progress of conditioned place preference. Methods: Morphine induced CPP acquisition, extinction and drug primed reinstatement model was established, and CREB expression in each brain area was measured by Western Blot methods. Results: Eight alternating injections of morphine (10 mg/kg) induced CPP, and 8 d saline extinction training that extinguished CPP. CPP was reinstated following a priming injection of morphine (2.5 mg/kg). During the phases of CPP acquisition and reinstatement, the level of CREB expression was significantly changed in different brain areas. Conclusion: It was proved that CPP model can be used as an effective tool to investigate the mechanisms underlying drug-induced reinstatement of drug seeking after extinction, and that morphine induced CPP and drug primed reinstatement may involve acti-vation of the transcription factor CREB in several brain areas, suggesting that the CREB and its target gene regulation pathway may mediate the basic mechanism underlying opioid dependence and its drug seeking behavior.

Inactivation of ERK1/2-CREB Pathway Is Implicated in MK801-induced Cognitive Impairment

Objective Schizophrenia(SZ)is associated with cognitive impairment,and it is known that the activity of cAMP response element binding protein(CREB)decreases in the brain of SZ patients.The previous study conducted by the investigators revealed that the upregulation of CREB improves the MK801-related SZ cognitive deficit.The present study further investigates the mechanism on how CREB deficiency is associated with SZ-related cognitive impairment.Methods MK-801 was used to induce SZ in rats.Western blotting and immunofluorescence were performed to investigate CREB and the CREB-related pathway implicated in MK801 rats.The long-term potentiation and behavioral tests were performed to assess the synaptic plasticity and cognitive impairment,respectively.Results The phosphorylation of CREB at Ser133 decreased in the hippocampus of SZ rats.Interestingly,among the upstream kinases of CREB,merely ERK1/2 was downregulated,while CaMKII and PKA remained unchanged in the brain of MK801-related SZ rats.The inhibition of ERK1/2 by PD98059 reduced the phosphorylation of CREB-Ser133,and induced synaptic dysfunction in primary hippocampal neurons.Conversely,the activation of CREB attenuated the ERK1/2 inhibitor-induced synaptic and cognitive impairment.Conclusion These present findings partially suggest that the deficiency of the ERK1/2-CREB pathway is involved in MK801-related SZ cognitive impairment.The activation of the ERK1/2-CREB pathway may be therapeutically useful for treating SZ cognitive deficits.

Activation of extracellular signal-regulated kinase in the anterior cingulate cortex contributes to the induction of long-term potentiation in rats

Objective To explore the role of the extracellular signal-regulated kinase （ERK）/cAMP response element binding protein （CREB） pathway in the induction of long-term potentiation （LTP） in the anterior cingulate cortex （ACC） that may be implicated in pain-related negative emotion. Methods LTP of field potential was recorded in ACC slice and the expressions of phospho-ERK （pERK） and phospho-CREB （pCREB） were examined using immunohistochemistry method. Results LTP could be induced stably in ACC slice by high frequency stimulation （2-train, 100 Hz, 1 s）, while APv （an antagonist of NMDA receptor） could block the induction of LTP in the ACC, indicating that LTP in this experiment was NMDA receptor-dependent. Bath application of PD98059 （50 μmol/L）, a selective MEK inhibitor, at 30 min before tetanic stimulation could completely block the induction of LTP. Moreover, the protein level of pERK in the ACC was transiently increased after LTP induction, starting at 5 rain and returning to basal at 1 h after tetanic stimulation. The protein level of pCREB was also increased after LTP induction. The up-regulation in pERK and pCREB expressions could be blocked by pretreatment of PD98059. Double immunostaining showed that after LTP induction, most pERK was co-localized with pCREB. Conclusion NMDA receptor and ERK-CREB pathway are necessary for the induction of LTP in rat ACC and may play important roles in pain emotion.

Metabolic regulation by salt inducible kinases

In fasting mammals,the liver is the primary source of glucose production for maintenance of normoglycemia.In this setting,circulating peptide hormones and catecholamines cause hepatic glucose output by stimulating glycogen breakdown as well as de novo glucose production through gluconeogenesis.Fasting gluconeogenesis is regulated by a complex transcriptional cascade culminating in elevated expression of hepatic enzymes that promote gluconeogenesis and glucose export to the blood.The cAMP response element binding protein CREB and its co-activator CRTC2 play crucial roles in signal-dependent transcriptional regulation of gluconeogenesis.Recent work has identified a family of serine/threonine kinases,the salt inducible kinases(SIKs),which are subject to hormonal control and constrain gluconeogenic and lipogenic gene expression in liver.As normal regulation of gluconeogenesis and lipogenesis is disrupted in diabetic states,SIK kinases are poised to serve as therapeutic targets to modulate metabolic disturbances in diabetic patients.The purpose of this review is to 1)describe the identification of CRTCs CREB co-activators and their regulation by SIKs,2)discuss recent progress toward understanding regulation and function of SIKs in metabolism and 3)examine the potential clinical impact of therapeutics that target SIK kinase function.