Mitogen-activated protein kinase p38 and MK2, MK3 and MK5: Ménage à trois or ménage à quatre?

The mitogen-activated protein kinase (MAPK) signalling pathways play pivotal roles in cellular processes such as proliferation, apoptosis, gene regulation, differentiation, and cell motility. The typical mammalian MAPK pathways ERK1/2, JNK, p38^MAPK, and ERK5 operate through a concatenation of three successive phosphorylation events mediated by a MAPK kinase kinase, a MAPK kinase, and a MAPK. MAPKs phosphorylate substrates with distinct functions, including other protein kinases referred to as MAPK-activated protein kinases. One family of related MAPK-activated protein kinases includes MK2, MK3, and MK5. While it is generally accepted that MK2 and MK3 are bona fide substrates for p38^MAPK, the genuineness of MK5 as a p38^MAPK substrate is disputed. This review summarizes the findings pro and contra an authentic p38^MAPK-MK5 relationship, discusses possible explanations for these discrepancies, and proposes experiments that may help to unequivocally clarify whether MK5 is indeed a substrate for p38^MAPK.     

Lectin from Canavalia brasiliensis (ConBr) protects hippocampal slices against glutamate neurotoxicity in a manner dependent of PI3K/Akt pathway

The excitotoxicity induced by excessive activation of the glutamatergic neurotransmission pathway is involved in several neuropathologies. In this sense, molecules that prevent the release of glutamate or the excessive activation of its receptors can be useful in preventing the neuronal cell death observed in these diseases. Lectins are proteins capable of reversible binding to the carbohydrates in glycoconjugates, and some have been used in the study and purification of glutamate receptors. ConBr is a mannose/glucose-binding lectin purified from Canavalia brasiliensis seeds. In the present study, we aimed to evaluate the neuroprotective activity of ConBr against glutamate-induced excitotoxicity. Hippocampal slices were isolated from adult male mice and incubated for 6 h in Krebs saline/DMEM buffer alone (control), in the presence of glutamate or glutamate plus ConBr. The phosphorylation of Akt and mitogen activated protein kinases (MAPKs) such as ERK1/2, p38^MAPK and JNK1/2/3 was evaluated with western blotting. The results indicate that glutamate provoked a reduction in the hippocampal slice viability (−25%), diminished the phosphorylation of Akt and augmented p38^MAPK and ERK1 phosphorylation. No changes were observed in the phosphorylation of JNK1/2/3 or ERK2. Notably, ConBr, through a mechanism dependent on carbohydrate interaction, prevented the reduction of cell viability and Akt phosphorylation induced by glutamate. Furthermore, in the presence of the PI3K inhibitor LY294002, ConBr was unable to reverse glutamate neurotoxicity. Taken together, our data suggest that the neuroprotective effect of ConBr against glutamate neurotoxicity requires oligosaccharide interaction and is dependent on the PI3K/Akt pathway.     

Evaluation of antidepressant-like activity of aqueous and ethanolic extracts of Terminalia bellirica Roxb. fruits in mice

The present study was undertaken to investigate the effect of aqueous and ethanolic extracts of T. bellirica on depression in mice using forced swim test (FST) and tail suspension test (TST). The extracts were administered orally for 10 successive days in separate groups of Swiss young male albino mice. Aqueous extract (50, 100 and 200 mg/kg) in a dose-dependent manner and ethanolic extract (100 mg/kg) significantly reduced the immobility time of mice in both FST and TST. The extracts were without any significant effect on locomotor activity of mice. The efficacies of aqueous extract (200 mg/kg) and ethanolic extract (100 mg/kg) were found to be similar to that of imipramine (15 mg/kg, po) and fluoxetine (20 mg/kg, po) administered for 10 successive days. Both extracts reversed reserpine-induced extension of immobility period of mice in FST and TST. Prazosin (62.5 microg/kg, ip; an alpha1-adrenoceptor antagonist), sulpiride (50 mg/kg, ip; a selective D2 receptor antagonist) and p-chlorophenylalanine (100 mg/kg, ip; an inhibitor of serotonin synthesis) significantly attenuated the aqueous and ethanolic extract-induced antidepressant-like effect in TST. Thus, both the aqueous and ethanolic extracts of T. bellirica elicited a significant antidepressant-like effect in mice by interaction with adrenergic, dopaminergic and serotonergic systems.     

Subchronic Oral Administration of Benzo[a]pyrene Impairs Motor and Cognitive Behavior and Modulates S100B Levels and MAPKs in Rats

Benzo[a]pyrene (BaP) is an environmental contaminant produced during incomplete combustion of organic material that is well known as a mutagenic and carcinogenic toxin. There are few studies addressing the molecular and cellular basis of behavioural alterations related to BaP exposure. The aim of this study was to evaluate the effect of subchronic oral administration of BaP on behavioral and neurochemical parameters. Wistar male rats received BaP (2 mg/kg) or corn oil (control), once a day for 28 days (n = 12/group). Spontaneous locomotor activity and short- and long-term memories were evaluated. Glial fibrillary acid protein and S100B content in the hippocampus, serum and CSF were measured using ELISA and total and phosphorylated forms of mitogen activated protein kinases (MAPKs) named extracellular signal-regulated kinases 1 and 2, p38^MAPK and c-Jun amino-terminal kinases 1 and 2, in the hippocampus, were evaluated by western blotting. BaP induced a significant increase on locomotor activity and a decrease in short-term memory. S100B content was increased significantly in cerebrospinal fluid. BaP induced a decrease on ERK2 phosphorylation in the hippocampus. Thus, BaP subchronic treatment induces an astroglial response and impairs both motor and cognitive behavior, with parallel inhibition of ERK2, a signaling enzyme involved in the hippocampal neuroplasticity. All these effects suggest that BaP neurotoxicity is a concern for environmental pollution.     

Atorvastatin Prevents Glutamate Uptake Reduction Induced by Quinolinic Acid Via MAPKs Signaling

Statins have been shown to promote neuroprotection in a wide range of neurological disorders. However, the mechanisms involved in such effects of statins are not fully understood. Quinolinic acid (QA) is a neurotoxin that induces seizures when infused in vivo and promotes glutamatergic excitotoxicity in the central nervous system. The aim of this study was to evaluate the putative glutamatergic mechanisms and the intracellular signaling pathways involved in the atorvastatin neuroprotective effects against QA toxicity. Atorvastatin (10 mg/kg) treatment for 7 days prevented the QA-induced decrease in glutamate uptake, but had no effect on increased glutamate release induced by QA. Moreover, atorvastatin treatment increased the phosphorylation of ERK1 and prevented the decrease in Akt phosphorylation induced by QA. Neither atorvastatin treatment nor QA infusion altered glutamine synthetase activity or the levels of phosphorylation of p38^MAPK or JNK1/2 during the evaluation. Inhibition of MEK/ERK signaling pathway, but not PI3K/Akt signaling, abolished the neuroprotective effect of atorvastatin against QA-induced decrease in glutamate uptake. Our data suggest that atorvastatin protective effects against QA toxicity are related to modulation of glutamate transporters via MAPK/ERK signaling pathway.     

Differential Activation of Mitogen-Activated Protein Kinases,ERK 1/2, p38MAPK and JNK p54/p46 During Postnatal Development of Rat Hippocampus

Mitogen-activated protein kinases (MAPKs) are a group of serine-threonine kinases, including p38^MAPK, ERK 1/2 and JNK p54/p46, activated by phosphorylation in response to extracellular stimuli. The early postnatal period is characterized by significant changes in brain structure as well as intracellular signaling. In the hippocampus MAPKs have been involved in the modulation of development and neural plasticity. However, the temporal profile of MAPK activation throughout the early postnatal development is incomplete. An understanding of this profile is important since slight changes in the activity of these enzymes, in response to environmental stress in specific developmental windows, might alter the course of development. The present study was undertaken to investigate the hippocampal differential activation of MAPK during postnatal period. MAPK activation and total content were evaluated by Western blotting of hippocampal tissue obtained from male Wistar rats at postnatal days (P) 1, 4, 7, 10, 14, 21, 30 and 60. The total content and phosphorylation of each MAPK was expressed as mean ± SEM and then calculates as a percentile compared to P1 (set at 100 %). The results showed: (1) phosphorylation peaks of p38^MAPK at PN4 (p = 0.036) and PN10 to PN60; (2) phosphorylation of ERK1 and ERK2 were increased with age (ERK1 p = 0.0000005 and ERK2 p = 0.003); (3) phosphorylation profile of JNK p54/p46 was not changed during the period analyzed (JNKp56 p = 0.716 and JNKp46 p = 0.192). Therefore, the activity profile of ERK 1/2 and p38^MAPK during postnatal development of rat hippocampus are differentially regulated. Our results demonstrate that ERK 1/2 and p38^MAPK are dynamically regulated during postnatal neurodevelopment, suggesting temporal correlation of MAPK activity with critical periods when programmed cell death and synaptogenesis are occurring. This suggests an important role for these MAPKs in postnatal development of rat hippocampus.

     

Eosinophil migration induced by mast cell chymase is mediated by extracellular signal-regulated kinase pathway

Mast cell chymase is known to induce eosinophil migration in vivo and in vitro. In the present study, we investigated possible involvement of mitogen-activated protein (MAP) kinases; extracellular signal-regulated kinase (ERK), c-Jun amino-terminal kinase (JNK), and p38, in the chymase-induced eosinophil migration. Human chymase induced a rapid phosphorylation of ERK1/2 and p38 in human eosinophilic leukemia EoL-1 cells, while no phosphorylation was detected in JNK. The chymase-induced phosphorylation of ERK and p38 was inhibited by pertussis toxin. Similar results were obtained in the experiments using mouse chymase and eosinophils. U0126 (the inhibitor for MAP/ERK kinase) suppressed chymase-induced migration of EoL-1 cells and mouse eosinophils. However, SB203580 (p38 inhibitor) and SP600125 (JNK inhibitor) showed little effect on the migration. It is suggested therefore that chymase activates ERK and p38 probably through G-protein-coupled receptor, and that ERK but not p38 cascade may have a crucial role in chymase-induced migration of eosinophils.     

Distinct roles of MK2 and MK5 in cAMP/PKA- and stress/p38MAPK-induced heat shock protein 27 phosphorylation

Background

Classical mammalian mitogen-activated protein kinase (MAPK) pathways consist of a cascade of three successive phosphorylation events resulting in the phosphorylation of a variety of substrates, including another class of protein kinases referred to as MAPK-activating protein kinases (MAPKAPKs). The MAPKAPKs MK2, MK3 and MK5 are closely related, but MK2 and MK3 are the major downstream targets of the p38^MAPK pathway, while MK5 can be activated by the atypical MAPK ERK3 and ERK4, protein kinase A (PKA), and maybe p38^MAPK. MK2, MK3, and MK5 can phosphorylate the common substrate small heat shock protein 27 (HSP27), a modification that regulates the role of HSP27 in actin polymerization. Both stress and cAMP elevating stimuli can cause F-actin remodeling, but whereas the in vivo role of p38^MAPK-MK2 in stress-triggered HSP27 phosphorylation and actin reorganization is well established, it is not known whether MK2 is involved in cAMP/PKA-induced F-actin rearrangements. On the other hand, MK5 can phosphorylate HSP27 and cause cytoskeletal changes in a cAMP/PKA-dependent manner, but its role as HSP27 kinase in stress-induced F-actin remodeling is disputed. Therefore, we wanted to investigate the implication of MK2 and MK5 in stress- and PKA-induced HSP27 phosphorylation.

Results

Using HEK293 cells, we show that MK2, MK3, and MK5 are expressed in these cells, but MK3 protein levels are very moderate. Stress- and cAMP-elevating stimuli, as well as ectopic expression of active MKK6 plus p38^MAPK or the catalytic subunit of PKA trigger HSP27 phosphorylation, and specific inhibitors of p38^MAPK and PKA prevent this phosphorylation. Depletion of MK2, but not MK3 and MK5 diminished stress-induced HSP27 phosphorylation, while only knockdown of MK5 reduced PKA-induced phosphoHSP27 levels. Stimulation of the p38^MAPK, but not the PKA pathway, caused activation of MK2.

Conclusion

Our results suggest that in HEK293 cells MK2 is the HSP27 kinase engaged in stress-induced, but not cAMP-induced phosphorylation of HSP27, while MK5 seems to be the sole MK to mediate HSP27 phosphorylation in response to stimulation of the PKA pathway. Thus, despite the same substrate specificity towards HSP27, MK2 and MK5 are implicated in different signaling pathways causing actin reorganization.     

Insulin regulates MAP kinase phosphatase-1 induction in Hirc B cells via activation of both extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK)

Previously, we have reported that insulin induces the expression of the dual-specificity tyrosine phosphatase Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) and that this may represent a negative feedback mechanism to regulate insulin-stimulated MAP kinase activity. In this work, the mechanism of regulation of MKP-1 expression by insulin was examined, particularly the role of the MAP kinase superfamily. Inhibition of the ERK pathway attenuated insulin-stimulated MKP-1 mRNA expression. Expression of dominant negative molecules of the JNK pathway also abolished insulin-stimulated MKP-1 expression. However, inhibition of p38^MAPK activity by SB202190 had no effect on insulin-stimulated MKP-1 induction. Simultaneous inhibition of the ERK and JNK pathways abolished the ability of insulin to stimulate MKP-1 expression, however, this combined inhibition was neither additive nor synergistic, suggesting these pathways converge to act on a common final effector. In conclusion, induction of MKP-1 mRNA expression in Hirc B cells by insulin requires activation of both the ERK and JNK pathways, but not p38^MAPK.     

The antidepressant-like effect of inosine in the FST is associated with both adenosine A1 and A2A receptors

Inosine is an endogenous purine nucleoside, which is formed during the breakdown of adenosine. The adenosinergic system was already described as capable of modulating mood in preclinical models; we now explored the effects of inosine in two predictive models of depression: the forced swim test (FST) and tail suspension test (TST). Mice treated with inosine displayed higher anti-immobility in the FST (5 and 50 mg/kg, intraperitoneal route (i.p.)) and in the TST (1 and 10 mg/kg, i.p.) when compared to vehicle-treated groups. These antidepressant-like effects started 30 min and lasted for 2 h after intraperitoneal administration of inosine and were not accompanied by any changes in the ambulatory activity in the open-field test. Both adenosine A₁ and A_2A receptor antagonists prevented the antidepressant-like effect of inosine in the FST. In addition, the administration of an adenosine deaminase inhibitor (1 and 10 mg/kg, i.p.) also caused an antidepressant-like effect in the FST. These results indicate that inosine possesses an antidepressant-like effect in the FST and TST probably through the activation of adenosine A₁ and A_2A receptors, further reinforcing the potential of targeting the purinergic system to the management of mood disorders.     

Telmisartan attenuates aortic hypertrophy in hypertensive rats by the modulation of ACE2 and profilin-1 expression

Profilin-1 has recently been linked to vascular hypertrophy and remodeling. Here, we assessed the hypothesis that angiotensin (Ang) II type I receptor antagonist telmisartan improves vascular hypertrophy by modulation of expression of profilin-1 and angiotensin-converting enzyme 2 (ACE2). Ten-week-old male spontaneously hypertensive rats (SHR) were received oral administration of telmisartan (5 or 10 mg/kg; daily) or saline for 10 weeks. Compared with Wistar–Kyoto (WKY) rats, there were marked increases in systolic blood pressure and profilin-1 expression and reduced ACE2 and peroxisome proliferator activated receptor-γ (PPARγ) levels in aorta of SHR, associated with elevated extracellular-signal regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) phosphorylation signaling and aortic hypertrophy characterized with increased media thickness, which were strikingly reversed by telmisartan. In cultured human umbilical artery smooth muscle cells (HUASMCs), Ang II induced a dose-dependent increase in profilin-1 expression, along with decreased ACE2 protein expression and elevated ERK1/2 and JNK phosphorylation. In addition, blockade of ERK1/2 or JNK by either specific inhibitor was able to abolish Ang II-induced ACE2 downregulation and profilin-1 upregulation in HUASMCs. Importantly, treatment with telmisartan (1 or 10 μM) or recombinant human ACE2 (2 mg/ml) largely ameliorated Ang II-induced profilin-1 expression and ERK1/2 and JNK phosphorylation and augmented PPARγ ?expression in the cultured HUASMCs. In conclusion, telmisartan treatment attenuates vascular hypertrophy in SHR by the modulation of ACE2 and profilin-1 expression with a marked reversal of ERK1/2 and JNK phosphorylation signaling pathways.     

Mechanism of cell death of rat cardiac fibroblasts induced by serum depletion

Serum starvation has recently been shown to cause cell death of cardiac fibroblasts and increased synthesis of extracellular matrix proteins in the surviving cells. In the present study, events occurring in the dying cells were investigated. Cultured adult rat cardiac fibroblasts were exposed to serum-free medium. Cell number was measured using a Coulter Counter Channelyzer. The activity of the extracellular signal-regulated or mitogen-activated protein kinases (ERK1/2, p42/p44^MAPK), the p38 kinase (p38^MAPK), the c-Jun N-terminal kinases (p46/p54^JNK), and Akt kinase was assessed by Western blotting and phospho-specific antibodies. Caspase 7-cleavage was investigated by Western blotting and specific antibodies. Caspase 3 activity was measured by detection of its cleaved substrate. The appearance of necrosis was studied by inclusion of trypan blue. Apoptosis was assessed by DNA ladder formation. The mRNA expression of Bax and Bcl-2 was investigated by quantitative real-time PCR. Serum withdrawal led to the death of 26% of cultured isolated cardiac fibroblasts during the first 5 h. The activity of the p42/p44^MAPK as well as of Akt kinase was partially reduced. For p46/p54^JNK and p38^MAPK, elevated phosphorylation was measured. Inhibition of p46/p54^JNK and p38^MAPK activity by SB202190 did not affect the decrease in cell number. Cleavage of caspase7 was detected after 90 min. However, no activation of caspase 3 was measured. DNA fragmentation was not found after serum depletion. Trypan blue staining, however, was observed in 16% of the cells after 5 h. The mRNA levels of both Bax and Bcl-2 were increased after 30 min. These results indicate the appearance of necrosis during serum starvation in cardiac fibroblasts. However, some processes typical of apoptosis were also detected.     

STRIP2 silencing inhibits vascular smooth muscle cell proliferation and migration via P38–AKT–MMP-2 signaling pathway

STRIP2 (FAM40B) was reported to regulate tumor cell migration. Our study aims to discuss the effect of STRIP2 in mouse aortic smooth muscle cell (MOVAS) proliferation and migration processes, which contributes greatly to atherosclerosis formation. In MOVAS cells, STRIP2 depletion suppressed cell proliferation and migration, which were related to a remarkable decrease in matrix metalloproteinases-2 (MMP-2)/MMP-9 expression. Additionally, P38 mitogen-activated protein kinases and Protein kinase B (AKT) are inactivated while extracellular signal-regulated kinase (ERK1/2) and jun N-terminal kinase (JNK) are activated upon STRIP2 silencing. SB203580 (P38 inhibitor) further reduced AKT phosphorylation (p-AKT) while dehydrocorydaline chloride (Dc; P38 activator) reversed this effect. Furthermore, Dc significantly recovered MMP-2 expression in STRIP2-knockdown cells. As expected, overexpressing STRIP2 exhibited a contrary effect. Dc and AKT activator SC79 reversed the inhibition of cell proliferation and migration induced by STRIP2 silencing. Interestingly, STRIP2 depletion increased vascular endothelial growth factor level significantly. Taken together, STRIP2 contributed to cell proliferation and migration through P38–AKT–MMP-2 signaling in MOVAS cells, indicating the importance of STRIP2 in atherosclerosis.     

Tauroursodeoxycholic Acid Mitigates High Fat Diet-Induced Cardiomyocyte Contractile and Intracellular Ca2+ Anomalies

ObjectivesThe endoplasmic reticulum (ER) chaperone tauroursodeoxycholic acid (TUDCA) has exhibited promises in the treatment of obesity, although its impact on obesity-induced cardiac dysfunction is unknown. This study examined the effect of TUDCA on cardiomyocyte function in high-fat diet-induced obesity.MethodsAdult mice were fed low or high fat diet for 5 months prior to treatment of TUDCA (300 mg/kg. i.p., for 15d). Intraperitoneal glucose tolerance test (IPGTT), cardiomyocyte mechanical and intracellular Ca²⁺ property, insulin signaling molecules including IRS-1, Akt, AMPK, ACC, GSK-3β, c-Jun, ERK and c-Jun N terminal kinase (JNK) as well as ER stress and intracellular Ca²⁺ regulatory proteins were examined. Myocardial ultrastructure was evaluated using transmission electron microscopy (TEM).ResultsHigh-fat diet depressed peak shortening (PS) and maximal velocity of shortening/relengthenin as well as prolonged relengthening duration. TUDCA reversed or overtly ameliorated high fat diet-induced cardiomyocyte dysfunction including prolongation in relengthening. TUDCA alleviated high-fat diet-induced decrease in SERCA2a and phosphorylation of phospholamban, increase in ER stress (GRP78/BiP, CHOP, phosphorylation of PERK, IRE1α and eIF2α), ultrastructural changes and mitochondrial permeation pore opening. High-fat diet feeding inhibited phosphorylation of AMPK and promoted phosphorylation of GSK-3β. TUDCA prevented high fat-induced dephosphorylation of AMPK but not GSK-3β. High fat diet promoted phosphorylation of IRS-1 (Ser³⁰⁷), JNK, and ERK without affecting c-Jun phosphorylation, the effect of which with the exception of ERK phosphorylation was attenuated by TUDCA.ConclusionsThese data depict that TUDCA may ameliorate high fat diet feeding-induced cardiomyocyte contractile and intracellular Ca²⁺ defects through mechanisms associated with mitochondrial integrity, AMPK, JNK and IRS-1 serine phosphorylation.     

Gamma-hydroxybutyrate reduces mitogen-activated protein kinase phosphorylation via GABA B receptor activation in mouse frontal cortex and hippocampus

gamma-Hydroxybutyrate (GHB) naturally occurs in the brain, but its exogenous administration induces profound effects on the central nervous system in animals and humans. The intracellular signaling mechanisms underlying its actions remain unclear. In the present study, the effects of GHB on the activation (phosphorylation) of mitogen-activated protein kinases (MAP kinases), extracellular signal-regulated kinase 1 and 2 (ERK1/2), were investigated. Acute administration of GHB (500 mg/kg, intraperitoneal) induced a fast and long lasting inhibition of MAP kinase phosphorylation in both frontal cortex and hippocampus. The reduced MAP kinase phosphorylation was observed in the CA1 and CA3 areas but not in the dentate gyrus. Pretreatment with the specific gamma-aminobutyric acid, type B (GABAB), receptor antagonist CGP56999A (20 mg/kg, intraperitoneal) prevented the action of GHB, and the effect of GHB was mimicked by baclofen, a selective GABAB receptor agonist, whereas the high affinity GHB receptor antagonist NCS-382 (200 mg/kg, intraperitoneal) had no effect on GHB-inhibited MAP kinase phosphorylation. Moreover, the GHB dehydrogenase inhibitor valproate (500 mg/kg, intraperitoneal), which inhibits the conversion of GHB into GABA, failed to block the effect of GHB on MAP kinase phosphorylation. Altogether, these data suggest that GHB, administered in vivo, reduces MAP kinase phosphorylation via a direct activation of GABAB receptors by GHB. In contrast, GHB (10 mm for 15 min) was found ineffective on MAP kinase phosphorylation in brain slices, indicating important differences in the conditions required for the second messenger activating action of GHB.     

c-jun amino-terminal kinase and mitogen activated protein kinase 1/2 mediate hepatocyte growth factor-induced migration of brain endothelial cells

Hepatocyte growth factor (HGF) influences several components of the angiogenic response, including endothelial cell migration. While recent studies indicate a crucial role of HGF in brain angiogenesis, the signaling pathways that regulate brain endothelial cell migration by HGF remain uncharacterized. Herein, we report that HGF stimulated human brain microvascular endothelial cell (HBMEC) migration in a dose- and time-dependent manner. Challenge of HBMECs with HGF activated the c-jun amino-terminal kinase (JNK), increased phosphorylation of the proline-rich tyrosine kinase 2 (Pyk-2) at Tyr(402) and activated c-Src. Inhibition of JNK by SP600125 or expression of a dominant negative JNK1 construct abrogated the migratory response of HBMECs to HGF. Treatment of HBMECs with the Src inhibitor PP2 markedly decreased HGF-stimulated JNK activation and migration to HGF. Moreover, expression of a mutant Pyk-2 construct prevented HGF-induced Pyk-2 phosphorylation at Tyr(402) and stimulation of HBMEC migration. Next, we examined activation of the extracellular signal regulated kinase (ERK) pathway. Stimulation of HBMECs by HGF led to rapid activation of ERK1/2, phosphorylation of Raf-1 at Ser(338) and Tyr(340/341) and MEK1/2 at Ser(222). Moreover, inhibition of ERK activation by UO126 and PD98059 markedly decreased HGF-stimulated HBMEC migration. HGF also activated AKT, while inhibition of AKT by LY294002 induced a modest decrease of HGF-induced HBMEC migration. These results highlight a model whereby JNK and ERK play a critical role in regulation of brain endothelial cell migration by HGF.     

Licorisoflavan A Exerts Antidepressant-Like Effect in Mice: Involvement of BDNF-TrkB Pathway and AMPA Receptors

Depression is a highly debilitating and life-threatening psychiatric disorder. The classical antidepressants are still not adequate due to undesirable side effects. Therefore, the development of new drugs for depression treatment is an urgent strategic to achieving clinical needs. Licorisoflavan A is a bioactive ingredient isolated from Glycyrrhizae Radix and has been recently reported for neuroprotective effects. In this study, the antidepressant-like effect and neural mechanism of licorisoflavan A were explored. In the mice behavioral despair test, we observed that licorisoflavan A exhibited powerful antidepressant-like effect in forced swimming test (FST), tail suspension test (TST), without affecting locomotor activity in open field test (OFT). Additionally, licorisoflavan A administration significantly restored Chronic mild stress (CMS)-induced changes in sucrose preference test (SPT), FST, and TST, without altering the locomotion in OFT. In chronical-stimulated mice, the licorisoflavan A treatment effectively attenuated the expressions of Brain-derived neurotrophic factor (BDNF), tyrosine kinase B (TrkB), the phosphorylations of cAMP response element binding protein (CREB), extracellular signal-regulated kinase (ERK)-1/2, eukaryotic elongation factor 2 (eEF2), mammalian target of rapamycin (mTOR), initiation factor 4E-binding protein 1 (4E-BP-1), and p70 ribosomal protein S6 kinase (p70S6K) in hippocampus of CMS-induced mice. Additionally, licorisoflavan A could reverse the decreases in synaptic proteins post-synaptic density protein 95 (PSD-95) and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor subunit glutamate receptor 1 (GluR1) caused by CMS, and its antidepressant-like effect was blocked by the AMPA receptor antagonist NBQX. These findings served as preclinical evidence that licorisoflavan A exerted potent antidepressant-like effects involving BDNF-TrkB pathway and AMPA receptors. Licorisoflavan A might be used as a potential medicine against depression-like disorder.

     

B7-H4 Treatment of T Cells Inhibits ERK, JNK, p38, and AKT Activation

B7-H4 is a newly identified B7 homolog that plays an important role in maintaining T-cell homeostasis by inhibiting T-cell proliferation and lymphokine-secretion. In this study, we investigated the signal transduction pathways inhibited by B7-H4 engagement in mouse T cells. We found that treatment of CD3(+) T cells with a B7-H4.Ig fusion protein inhibits anti-CD3 elicited T-cell receptor (TCR)/CD28 signaling events, including phosphorylation of the MAP kinases, ERK, p38, and JNK. B7-H4.Ig treatment also inhibited the phosphorylation of AKT kinase and impaired its kinase activity as assessed by the phosphorylation of its endogenous substrate GSK-3. Expression of IL-2 is also reduced by B7-H4. In contrast, the phosphorylation state of the TCR proximal tyrosine kinases ZAP70 and lymphocyte-specific protein tyrosine kinase (LCK) are not affected by B7-H4 ligation. These results indicate that B7-H4 inhibits T-cell proliferation and IL-2 production through interfering with activation of ERK, JNK, and AKT, but not of ZAP70 or LCK.