miR-142 downregulation alleviates the impairment of spatial learning and memory, reduces the level of apoptosis, and upregulates the expression of pCaMKII and BAI3 in the hippocampus of APP/PS1 transgenic mice

MicroRNA-142-5p (miR-142-5p) has been found to be dysregulated in several neurodegenerative disorders. However, little is known about the involvement of miR-142-5p in Alzheimer's disease (AD). Brain angiogenesis inhibitor 3 (BAI3), which belongs to the adhesion-G protein-coupled receptor subgroup, contributes to a variety of neuropsychiatric disorders. Despite its very high expression in neurons, the role of BAI3 in AD remains elusive, and its mechanism at the cellular and molecular levels needs to be further elucidated. The current study sought to investigate whether miR-142-5p influenced BAI3 expression and neuronal synaptotoxicity induced by Aβ, both in APP/PS1 transgenic mice and a cellular model of Alzheimer's disease. Altered expression of miR-142-5p was found in the hippocampus of AD mice. Inhibition of miR-142 could upregulate BAI3 expression, enhance neuronal viability and prevent neurons from undergoing apoptosis. In addition, the reduction of phosphorylation of Synapsin I and calcium/calmodulin-dependent protein kinase II (CaMKII), as well as the expression of PSD-95 in the hippocampus of APP/PS1 transgenic mice, were significantly restored by inhibiting miR-142. Meanwhile, the levels of Aβ_1-42, β-APP, BACE-1 and PS-1 in cultured neurons were detected, and the effects of inhibiting miR-142 on spatial learning and memory were also observed. Interestingly, we found that BAI3, an important regulator of excitatory synapses, was a potential target gene of miR-142-5p. Collectively, our findings suggest that miR-142 inhibition can alleviate the impairment of spatial learning and memory, reduce the level of apoptosis, and upregulate the expression of pCaMKII and BAI3 in the hippocampus of APP/PS1 transgenic mice; thus, appropriate interference of miR-142 may provide a potential therapeutic approach to rescue cognitive dysfunction in AD patients.

Physiological testosterone attenuates profibrotic activities of rat cardiac fibroblasts through modulation of nitric oxide and calcium homeostasis

Testosterone deficiency is associated with poor prognosis among patients with chronic heart failure (HF). Physiological testosterone improves the exercise capacity of patients with HF. In this study, we evaluated whether treatment with physiological testosterone contributes to anti-fibrogenesis by modifying calcium homeostasis in cardiac fibroblasts and we studied the underlying mechanisms. Nitric oxide (NO) analyses, calcium (Ca²⁺) fluorescence, and Western blotting were performed in primary isolated rat cardiac fibroblasts with or without (control cells) testosterone (10, 100, 1,000 nmol/L) treatment for 48 hours. Physiological testosterone (10 nmol/L) increased NO production and phosphorylation at the inhibitory site of the inositol trisphosphate (IP3) receptor, thereby reducing Ca²⁺ entry, phosphorylated Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) expression, type I and type III pro-collagen production. Non-physiological testosterone-treated fibroblasts exhibited similar NO and collagen production capabilities as compared to control (testosterone deficient) fibroblasts. These effects were blocked by co-treatment with NO inhibitor (L-NG-nitro arginine methyl ester [L-NAME], 100 μmol/L). In the presence of the IP3 receptor inhibitor (2-aminoethyl diphenylborinate [2-APB], 50 μmol/L), testosterone-deficient and physiological testosterone-treated fibroblasts exhibited similar phosphorylated CaMKII expression. When treated with 2-APB or CaMKII inhibitor (KN93, 10 μmol/L), testosterone-deficient and physiological testosterone-treated fibroblasts exhibited similar type I, and type III collagen production. In conclusion, physiological testosterone activates NO production, and attenuates the IP3 receptor/Ca²⁺ entry/CaMKII signaling pathway, thereby inhibiting the collagen production capability of cardiac fibroblasts.

Isoflurane triggers the acute cognitive impairment of aged rats by damaging hippocampal neurons via the NR2B/CaMKII/CREB pathway

Isoflurane was responsible for acute neuronal impairment, but its potential molecular mechanisms in damaging hippocampal neurons had not been clearly understood. This study aimed to explore the underlying mechanism of how isoflurane affected the cognitive function of aged rats by damaging the hippocampal neurons. Acute cognitive impairment was found in aged Wistar rats via Morris water maze test and Y-maze test after isoflurane anesthesia in a dose-dependent manner compared with the control group in vivo. Isoflurane also decreased the viabilities and strengthened the apoptotic potential of hippocampal neurons by damaging the mitochondria in a time-dependent manner compared with the control group which was reported by MTT, immunofluorescent assay, flow cytometry and western blot assay in vitro. Isoflurane jeopardized hippocampal neurons by directly inactivating the NR2B/CaMKII/CREB pathway and its harmful effects could be ameliorated by adding CaMKII activator CdCl₂. These findings provided evidence that the cognitive ability of aged rats was injured by isoflurane exposure and isoflurane also inhibited the viability and enhanced the apoptosis of hippocampal neurons by damaging the mitochondria through inhibition of the NR2B/CaMKII/CREB pathway and its harmful roles could be partially ameliorated by CdCl₂. Our study demonstrated that isoflurane could cause acute neuronal damage and we provided fresh insights that contributed to the safe use of anesthetic agents and the prevention of PND in elderly people.

Calcium/Calmodulin-Dependent Kinase (CaMKII) Inhibition Protects Against Purkinje Cell Damage Following CA/CPR in Mice

Ischemic brain damage is triggered by glutamate excitotoxicity resulting in neuronal cell death. Previous research has demonstrated that N-methly-D-aspartate (NMDA) receptor activation triggers downstream calcium-dependent signaling pathways, specifically Ca2+/calmodulin-dependent protein kinase II (CaMKII). Inhibiting CaMKII is protective against hippocampal ischemic injury, but there is little known about its role in the cerebellum. To examine the neuroprotective potential of CaMKII inhibition in Purkinje cells, we subjected C57BL/6 or CaMKIIα KO male mice (8-12 weeks old) to cardiac arrest followed by cardiopulmonary resuscitation (CA/CPR). We performed a dose-response study for tat-CN19o and cerebellar injury was analyzed at 7 days after CA/CPR. Acute signaling was assessed at 6 h after CA/CPR using Western blot analysis. We observed increased phosphorylation of the T286 residue of CaMKII, suggesting increased autonomous activation. Analysis of Purkinje cell density revealed a decrease in cell density at 7 days after CA/CPR that was prevented with tat-CN19o at doses of 0.1 and 1 mg/kg. However, neuroprotection in the cerebellum required doses that were 10-fold higher than what was needed in the hippocampus. CaMKIIα KO mice subjected to sham surgery or CA/CPR had similar Purkinje cell densities, suggesting CaMKIIα is required for CA/CPR-induced injury in the cerebellum. We also observed a CA/CPR-induced activation of death-associated protein kinase (DAPK1) that tat-CN19o did not block. In summary, our findings indicate that inhibition of autonomous CaMKII activity is a promising therapeutic approach that is effective across multiple brain regions.

Nandrolone administration with or without strenuous exercise increases cardiac fatal genes overexpression, calcium/calmodulin-dependent protein kinaseiiδ, and monoamine oxidase activities and enhances blood pressure in adult wistar rats

Misuse of anabolic androgenic steroids (AAS) increases prevalence of cardiovascular abnormalities in athletes, and the underlying molecular mechanism involved in those abnormalities continues to be investigated. The aim of this study was to investigate the effect of chronic nandrolone exposure on alpha and beta-myosin heavy chain (MHC) isoforms gene expression transition, blood pressure related parameters, calcium/calmodulin-dependent protein kinaseIIδ (CaMKIIδ), and monoamine oxidase (MAO) activities in rats' hearts. It was also planned to evaluate the effect of strenuous exercise on cardiac abnormalities induced by nandrolone. Thirty-two male wistar rats were assigned into four groups, namely control, nandrolone, nandrolone with strenuous exercise, and strenuous exercise groups. Nandrolone consumption significantly increased systolic, diastolic, pulse and dicrotic pressure, mean arterial pressure, as well as the amplitude of first peak (H1). Moreover, exercise combined with nandrolone completely masked this effect. The mRNA expression of β-MHC and the ratio of β -MHC/α -MHC showed a significant increase in the nandrolone and nandrolone with strenuous exercise groups compared to those in the control group. The values of heart tissue calcium/calmoldulin-dependent protein kinase IIδ (CaMKIIδ), and monoamine oxidase (MAO) in the nandrolone, nandrolone with strenuous exercise and exercise groups were significantly higher than those values in the control group. These findings indicate that nandrolone-induced heart and hemodynamic abnormalities may in part be associated with MHC isoform changes and Ca²⁺ homeostasis changes mediated by increased CaMKIIδ and MAO activities and that these effects can be provoked via strenuous exercise.

Memantine attenuated alcohol withdrawal-induced anxiety-like behaviors through down-regulating NR1-CaMKII-ERK signaling pathway

Alcohol abuse and anxiety disorders often occur concurrently, but their underlying cellular mechanisms remain unclear. N-methyl-D-aspartic acid receptors (NMDARs) have recently received attention from those interested in the neurobiology of anxiety. A chronic alcohol exposure rat model (28 consecutive days of 20% alcohol intake and 6 h of withdrawal) was established. Here, we investigated the NMDAR1 (NR1), Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinases (ERK) pathway in the modulation of anxiety-like behaviors in rats exposed to an open field and elevated plus maze (EPM) through systematic injections of memantine (a NMDAR inhibitor). We found that the NR1-CaMKII-ERK signaling pathway was activated after alcohol withdrawal in medial prefrontal cortex (mPFC) and nucleus accumbens shell (NAcSh) but not core (NAcC). Memantine treatment greatly ameliorated anxiety-like behavior in the rats experiencing alcohol withdrawal. Moreover, memantine uniformly suppressed the phosphorylation of NR1-CaMKII-ERK pathway induced by alcohol withdrawal. Our results suggest that activation of the NR1-CaMKII-ERK pathway in the mPFC and NAcSh is an important contributor to the molecular mechanisms underlying alcohol withdrawal-induced anxiety behaviors. NMDAR signaling pathway inhibitors are thus potential therapeutics for treating alcohol abuse.

Intestinal glucose-induced calcium-calmodulin kinase signaling in the gut-brain axis in awake rats

BACKGROUND

Lumenal glucose initiates changes in gastrointestinal (GI) function, including inhibition of gastric emptying, stimulation of pancreatic exocrine and endocrine secretion, and intestinal fluid secretion. Glucose stimulates the release of GI hormones and 5-hydroxytryptamine (5-HT), and activates intrinsic and extrinsic neuronal pathways to initiate changes in GI function. The precise mechanisms involved in luminal glucose-sensing are not clear; studying gut endocrine cells is difficult due to their sparse and irregular localization within the epithelium.

METHODS

Here we show a technique to determine activation of gut epithelial cells and the gut-brain pathway in vivo in rats using immunohistochemical detection of the activated, phosphorylated, form of calcium-calmodulin kinase II (pCaMKII).

KEY RESULTS

Perfusion of the gut with glucose (60 mg) increased pCaMKII immunoreactivity in 5-HT-expressing enterochromaffin (EC) cells, cytokeratin-18 immunopositive brush cells, but not in enterocytes or cholecystokinin-expressing cells. Lumenal glucose increased pCaMKII in neurons in the myenteric plexus and nodose ganglion, nucleus of the solitary tract, dorsal motor nucleus of the vagus and the arcuate nucleus. pCaMKII expression in neurons, but not in EC cells, was significantly attenuated by pretreatment with the 5-HT(3) R antagonist ondansetron. Deoxynojirimycin, a selective agonist for the putative glucose sensor, sodium-glucose cotransporter-3 (SGLT-3), mimicked the effects of glucose with increased pCaMKII in ECs and neurons; galactose had no effect.

CONCLUSIONS & INFERENCES

The data suggest that native EC cells in situ respond to glucose, possibly via SGLT-3, to activate intrinsic and extrinsic neurons and thereby regulate GI function.

Disruption of noncanonical Wnt/CA2+ pathway in the cadmium-induced omphalocele in the chick model

PURPOSE

Cadmium (Cd) has been found to cause ventral body wall defects (VBWDs) in the chick embryo similar to human omphalocele. The earliest detectable histologic changes in Cd-induced VBWD chick model have been observed 4 hours posttreatment. The exact mechanism by which Cd acts in the early embryogenesis remains unclear. Wnt proteins play a key role during embryogenesis, and altered Wnt signaling has been linked to developmental defects. Noncanonical Wnt/Ca(2+) pathway has been implicated in regulating embryogenesis by controlling cell movement and adhesion. Wnt11 can activate protein kinase C (PKC) and calcium/calmodulin-dependent kinase II (CaMKII) in the Wnt/Ca(2+) pathway. We hypothesized that the Wnt11, PKCalpha, and CaMKII gene expression is downregulated in the Cd-induced VBWD during early embryogenesis.

METHODS

After 60 hours of incubation, chick embryos were harvested 1 hour (1H), 4H, and 8H after treatment of saline or cadmium and divided into 2 groups: control and Cd (n = 8 at each time-point, respectively). Real-time polymerase chain reaction was performed to evaluate the messenger RNA (mRNA) expression of Wnt11, PKCalpha, and CaMKII in the Cd-induced VBWD chick model.

RESULTS

The mRNA expression levels of Wnt11, PKCalpha, and CaMKII were significantly decreased at 1H in Cd group compared to controls (P < .05). However, there were no significant differences in the other time-points.

CONCLUSION

Downregulation of Wnt11, PKCalpha, and CaMKII gene expression during the narrow window of early embryogenesis may cause VBWD, interfering with cell movement and adhesion, disrupting Wnt/Ca(2+) pathway.

Nifedipine inhibits cardiac hypertrophy and left ventricular dysfunction in response to pressure overload

Pathological hypertrophy is commonly induced by activation of protein kinases phosphorylating class II histone deacetylases (HDACs) and desuppression of transcription factors, such as nuclear factor of activated T cell (NFAT). We hypothesized that nifedipine, an L-type Ca(2+) channel blocker, inhibits Ca(2+) calmodulin-dependent kinase II (CaMKII) and NFAT, thereby inhibiting pathological hypertrophy. Mice were subjected to sham operation or transverse aortic constriction (TAC) for 2 weeks with or without nifedipine (10 mg/kg/day). Nifedipine did not significantly alter blood pressure or the pressure gradient across the TAC. Nifedipine significantly suppressed TAC-induced increases in left ventricular (LV) weight/body weight (BW; 5.09 +/- 0.80 vs. 4.16 +/- 0.29 mg/g, TAC without and with nifedipine, n = 6,6, p < 0.05), myocyte cross-sectional area (1,681 +/- 285 vs. 1,434 +/- 197 arbitrary units, p < 0.05), and expression of fetal-type genes, including atrial natriuretic factor (35. 9 +/- 6.4 vs. 8.6 +/- 3.3 arbitrary units, p < 0.05). TAC-induced increases in lung weight/BW (7.7 +/- 0.9 vs. 5.5 +/- 0.5 mg/g, p < 0.05) and decreases in LV ejection fraction (65.5 +/- 3.1% vs. 75.7 +/- 3.3%, p < 0.05) were attenuated by nifedipine. Nifedipine caused significant inhibition of TAC-induced activation of NFAT-mediated transcription, which was accompanied by suppression of Thr 286 phosphorylation in CaMKII. Nifedipine inhibited activation of CaMKII and NFAT by phenylephrine, accompanied by suppression of Ser 632 phosphorylation and nuclear exit of HDAC4 in cardiac myocytes. These results suggest that a subpressor dose of nifedipine inhibits pathological hypertrophy in the heart by inhibiting activation of CaMKII and NFAT, a signaling mechanism commonly activated in pathological hypertrophy.

Chronic caffeine treatment prevents sleep deprivation-induced impairment of cognitive function and synaptic plasticity

STUDY OBJECTIVES

This study was undertaken to provide a detailed account of the effect of chronic treatment with a small dose of caffeine on the deleterious effects of sleep loss on brain function in rats.

EXPERIMENTAL DESIGN

We investigated the effects of chronic (4 weeks) caffeine treatment (0.3 g/L in drinking water) on memory impairment in acutely (24 h) sleep-deprived adult male Wistar rats. Sleep deprivation was induced using the modified multiple platform model. The effects of caffeine on sleep deprivation-induced hippocampus-dependent learning and memory deficits were studied by 3 approaches: learning and memory performance in the radial arm water maze task, electrophysiological recording of early long-term potentiation (E-LTP) in area CA1 of the hippocampus, and levels of memory- and synaptic plasticity-related signaling molecules after E-LTP induction.

MEASUREMENT AND RESULTS

The results showed that chronic caffeine treatment prevented impairment of hippocampus-dependent learning, shortterm memory and E-LTP of area CA1 in the sleep-deprived rats. In correlation, chronic caffeine treatment prevented sleep deprivation-associated decrease in the levels of phosphorylated calcium/calmodulin-dependent protein kinase II (P-CaMKII) during expression of E-LTP.

CONCLUSIONS

The results suggest that long-term use of a low dose of caffeine prevents impairment of short-term memory and E-LTP in acutely sleep-deprived rats.

Recovery of network-driven glutamatergic activity in rat hippocampal neurons during chronic glutamate receptor blockade

Previous studies indicated that a long-term decrease in the activity of ionotropic glutamate receptors induces cholinergic activity in rat and mouse hypothalamic neuronal cultures. Here we studied whether a prolonged inactivation of ionotropic glutamate receptors also induces cholinergic activity in hippocampal neurons. Receptor activity was chronically suppressed in rat hippocampal primary neuronal cultures with two proportionally increasing sets of concentrations of NMDA plus non-NMDA receptor antagonists: 100 microM/10 microM AP5/CNQX (1X cultures) and 200 microM/20 microM AP5/CNQX (2X cultures). Using calcium imaging we demonstrate that cholinergic activity does not develop in these cultures. Instead, network-driven glutamate-dependent activity, that normally is detected in hyper-excitable conditions, reappears in each culture group in the presence of these antagonists and can be reversibly suppressed by higher concentrations of AP5/CNQX. This activity is mediated by non-NMDA receptors and is modulated by NMDA receptors. Further, non-NMDA receptors, the general level of glutamate receptor activity and CaMK-dependent signaling are critical for development of this network-driven glutamatergic activity in the presence of receptor antagonists. Using electrophysiology, western blotting and calcium imaging we show that some neuronal parameters are either reduced or not affected by chronic glutamate receptor blockade. However, other parameters (including neuronal excitability, mEPSC frequency, and expression of GluR1, NR1 and betaCaMKII) become up-regulated and, in some cases, proportionally between the non-treated, 1X and 2X cultures. Our data suggest recovery of the network-driven glutamatergic activity after chronic glutamate receptor blockade. This recovery may represent a form of neuronal plasticity that compensates for the prolonged suppression of the activity of glutamate receptors.