Effects of ethanol on the rat glutamate excitatory amino acid transporter type 3 expressed in Xenopus oocytes: role of protein kinase C and phosphatidylinositol 3-kinase

Background: Glutamate is a major excitatory neurotransmitter in the central nervous system. Glutamate transporters play a critical role in maintaining extracellular glutamate concentrations. We investigated the effects of ethanol on a neuronal glutamate transporter, excitatory amino acid transporter type 3 (EAAT3), and the role of protein kinase C (PKC) and phosphatidylinositol 3‐kinase (PI3 K) in mediating these effects. Methods: EAAT3 was expressed in Xenopus oocytes by injection of EAAT3 messenger RNA. By using a two‐electrode voltage clamp, membrane currents were recorded after the application of l‐glutamate. Responses were quantified by integration of the current trace and reported as microcoulombs. Data are mean ± SEM. Results: Ethanol enhanced EAAT3 activity in a concentration‐dependent manner. At 25, 50, 100, and 200 mM of ethanol, the responses were significantly increased compared with control values. Kinetic study demonstrated that ethanol (50 mM) significantly increased V_max (3.48 ± 0.2 μC for control versus 4.16 ± 0.24 μC for ethanol; n= 19; p < 0.05) without a significant change in the K_m (65.6 ± 11.1 μM for control versus 55.8 ± 9.6 μM for ethanol; n= 19; p > 0.05) of EAAT3 for glutamate. Preincubation of the oocytes with phorbol‐12‐myristate‐13‐acetate (PMA) significantly increased EAAT3 activity (0.98 ± 0.08 μC for control versus 1.28 ± 0.09 μC for ethanol; n= 19; p < 0.05). However, there was no statistical difference among the responses of EAAT3 to PMA, ethanol, or PMA plus ethanol. Although the PKC inhibitors chelerythrine and staurosporine did not decrease the basal EAAT3 activity, they abolished the enhancement of EAAT3 activity by ethanol. Pretreatment with wortmannin, a PI3 K inhibitor, also abolished the ethanol‐enhanced EAAT3 activity. Conclusions: These results suggest that acute ethanol exposure increases EAAT3 activity at clinically relevant concentrations and that PKC and PI3 K may be involved in mediating these ethanol effects.     

Inhibition of the activity of excitatory amino acid transporter 4 expressed in Xenopus oocytes after chronic exposure to ethanol

Background: The extracellular glutamate concentration is tightly controlled by excitatory amino acid transporters (EAATs). EAAT4 is the predominant EAAT in the cerebellar Purkinje cells. Purkinje cells play a critical role in motor coordination and may be an important target for ethanol to cause motor impairments. We designed this study to determine the effects of chronic ethanol exposure on the activity of EAAT4 and evaluate the involvement of protein kinase C (PKC) and phosphatidylinositol 3‐kinase (PI3K) in these effects. Methods: EAAT4 was expressed in Xenopus oocytes following injection of EAAT4 mRNA. Oocytes were incubated with ethanol‐containing solution for 24 to 96 hours. Membrane currents induced by l ‐aspartate were recorded using 2‐electrode voltage clamps. Responses were quantified by integration of the current trace and reported in microCoulombs (μC). Results: Ethanol dose‐ and time‐dependently reduced EAAT4 activity. EAAT4 activity after a 96‐hour exposure was significantly decreased compared to the control values at all concentrations tested (10 to 100 mM). Ethanol (50 mM) significantly decreased the Vmax (2.2 ± 0.2 μC for control vs. 1.6 ± 0.2 μC for ethanol, n = 18, p < 0.05) of EAAT4 for l ‐aspartate. Preincubation of ethanol‐treated (50 mM for 96 hours) oocytes with phorbol‐12‐myrisate‐13‐acetate (100 nM for 10 minutes) abolished the ethanol‐induced decrease in EAAT4 activity. While staurosporine (2 μM for 1 hour) or chelerythrine (100 μM for 1 hour) significantly decreased EAAT4 activity, no difference was observed in EAAT4 activity among the staurosporine, ethanol, or ethanol plus staurosporine groups. Similarly, EAAT4 activity did not differ among the chelerythrine, ethanol, or ethanol plus chelerythrine groups. Pretreatment of the oocytes with wortmannin (1 μM for 1 hour) also significantly decreased EAAT4 activity. However, no difference was observed in the wortmannin, ethanol, or ethanol plus wortmannin groups. Conclusions: The results of this study suggest that chronic ethanol exposure decreases EAAT4 activity and that PKC and PI3K may be involved in these effects. These effects of ethanol on EAAT4 may cause an increase in peri‐Purkinje cellular glutamate concentration, and may be involved in cerebellar dysfunction and motor impairment after chronic ethanol ingestion.     

Ethanol increases the activity of rat excitatory amino acid transporter type 4 expressed in Xenopus oocytes: role of protein kinase C and phosphatidylinositol 3-kinase

Background: Glutamate is the major excitatory neurotransmitter in the central nervous system and is critical for essentially all physiological processes, such as learning, memory, central pain transduction, and control of motor function. Excitatory amino acid transporters (EAATs) play a key role in regulating glutamate neurotransmission by uptake of glutamate into cells. EAAT4 is the major EAAT in the cerebellar Purkinje cells. The authors investigated the effects of ethanol on EAAT4 and the mediatory effects of protein kinase C (PKC) and phosphatidylinositol 3‐kinase (PI3K) in this context. Methods: Excitatory amino acid transporter 4 was expressed in Xenopus oocytes by injecting EAAT4 mRNA. l ‐aspartate‐induced membrane currents were measured using a two‐electrode voltage clamp. Responses were quantified by integrating current traces and are represented in microCoulombs (μC). Results: Ethanol increased EAAT4 activity in a dose‐dependent manner. At ethanol concentrations of 25, 50, 100, and 200 mM, the responses were significantly higher than untreated control values. Ethanol (25 mM) significantly increased the V_max (1.5 ± 0.1 μC for control vs. 2.0 ± 0.1 μC for ethanol, p < 0.05), but did not affect K_m (2.3 ± 0.6 μM for control vs. 1.7 ± 0.7 μM for ethanol, p > 0.05) of EAAT4 for l ‐aspartate. Preincubation of oocytes with phorbol‐12‐myristate‐13‐acetate (PMA, a PKC activator) significantly increased EAAT4 activity. However, combinations of PMA and ethanol versus PMA or ethanol alone did not increase responses further. Two PKC inhibitors, chelerythrine and staurosporine did not reduce basal EAAT4 activity but abolished ethanol‐enhanced EAAT4 activity. Pretreatment with wortmannin (a PI3K inhibitor) also abolished ethanol‐enhanced EAAT4 activity. Conclusions: These results demonstrate that acute ethanol exposure increases EAAT4 activity at clinically relevant concentrations and that PKC and PI3K may mediate this. The effects of ethanol on EAAT4 may play a role in the cerebellar dysfunction caused by ethanol intoxication.     

Inhibitory effects of ethanol on rat mesangial cell proliferation via protein kinase C pathway

A large body of evidence has shown that ethanol inhibits the cell growth and cell proliferation in a variety of cell types. However, it has not been studied whether ethanol inhibits the proliferation of mesangial cells (MC) in the kidney. We examined the effects of ethanol on cell proliferation in cultured rat MC. Treatment with ethanol (10-200 mM) for 48 hr inhibited [(3)H]thymidine incorporation into MC in a concentration-dependent manner. The same concentrations of ethanol also inhibited the increase in cell number of MC. GF109203X and chelerythrine chloride, inhibitors for protein kinase C, eliminated the inhibitory effects of ethanol; and protein kinase C activator, PMA, mimicked the effects of ethanol. In contrast, neither the protein kinase A inhibitor H-89 nor the protein kinase G inhibitor KT5823 had any effect. These findings suggest that ethanol has inhibitory effects on the proliferation of MC, probably via activation of the protein kinase C pathway.     

Acute ethanol administration rapidly increases phosphorylation of conventional protein kinase C in specific mammalian brain regions in vivo

BACKGROUND: Protein kinase C (PKC) is a family of isoenzymes that regulate a variety of functions in the central nervous system including neurotransmitter release, ion channel activity, and cell differentiation. Growing evidence suggests that specific isoforms of PKC influence a variety of behavioral, biochemical, and physiological effects of ethanol in mammals. The purpose of this study was to determine whether acute ethanol exposure alters phosphorylation of conventional PKC isoforms at a threonine 674 (p-cPKC) site in the hydrophobic domain of the kinase, which is required for its catalytic activity. METHODS: Male rats were administered a dose range of ethanol (0, 0.5, 1, or 2 g/kg, intragastric) and brain tissue was removed 10 minutes later for evaluation of changes in p-cPKC expression using immunohistochemistry and Western blot methods. RESULTS: Immunohistochemical data show that the highest dose of ethanol (2 g/kg) rapidly increases p-cPKC immunoreactivity specifically in the nucleus accumbens (core and shell), lateral septum, and hippocampus (CA3 and dentate gyrus). Western blot analysis further showed that ethanol (2 g/kg) increased p-cPKC expression in the P2 membrane fraction of tissue from the nucleus accumbens and hippocampus. Although p-cPKC was expressed in numerous other brain regions, including the caudate nucleus, amygdala, and cortex, no changes were observed in response to acute ethanol. Total PKCgamma immunoreactivity was surveyed throughout the brain and showed no change following acute ethanol injection. CONCLUSIONS: These results suggest that ethanol rapidly promotes phosphorylation of cPKC in limbic brain regions, which may underlie effects of acute ethanol on the nervous system and behavior.     

Effects of acamprosate on neuronal receptors and ion channels expressed in Xenopus oocytes

Background: Acamprosate (calcium acetylhomotaurinate) has proven to be a moderately effective pharmacological adjunct for the treatment of alcoholism. However, the central nervous system mechanism by which acamprosate reduces alcohol relapse remains unclear. Here we survey a number of metabotropic receptors, ligand‐gated ion channels, and voltage‐gated ion channels, to determine if acamprosate has actions at these sites in the central nervous system. Methods: Xenopus oocytes were injected with cDNAs or cRNAs encoding metabotropic glutamate receptors 1 and 5, M1 muscarinic receptors, glycine α1 homomeric and α1β1 heteromeric receptors, γ‐aminobutyric acid A (GABA_Aα4β3δ, α4β3γ2s, and α1β2γ2s) receptors, vanilloid receptor 1, and various combinations of α and β subunits of voltage‐gated Na⁺ channels. Electrophysiological responses were measured using two‐electrode voltage clamp parameters after activation with agonists or voltage steps (for the voltage‐gated channels). Acamprosate (0.1 to 100 μM) was pre‐applied for 1 minute, followed by co‐application with agonist. Acamprosate was also applied with ethanol to determine if it altered ethanol responses at some of these receptors and channels. Results: None of the receptors or ion channels responded to acamprosate alone. Acamprosate also failed to alter the activation of receptors or channels by agonists or after activation of voltage‐gated channels. There was no effect of acamprosate on ethanol responses at GABA_Aα1β2γ2s receptors or Na⁺ channels. Conclusions: Acamprosate does not significantly modulate the function of these receptors and ion channels at clinically relevant concentrations. Thus, the clinical effectiveness of acamprosate in the treatment of alcoholism is not likely due to direct effects on these receptors or ion channels.     

Increased consumption but not operant self-administration of ethanol in mice lacking the RIIbeta subunit of protein kinase A

BACKGROUND: Accumulating evidence indicates that adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) is involved in the neurobiological responses to ethanol. Previous reports indicate that mice lacking the RIIbeta subunit of PKA (RIIbeta(-/-)) voluntarily consume more ethanol than wild-type controls (RIIbeta(+/+)) using 2-bottle testing procedures. Although such procedures primarily measure consummatory behavior, operant self-administration procedures allow analysis of consummatory as well as appetitive or "ethanol-seeking" behavior (i.e., lever pressing is required to gain access to the ethanol solution). Therefore, we determined whether the high ethanol consumption characteristic of RIIbeta(-/-) mice would be complemented by increased appetitive ethanol-seeking behavior in an operant paradigm. METHODS: RIIbeta(-/-) (n=8) and RIIbeta(+/+) (n=8) mice were initially sucrose-faded until they were lever responding for nonsweetened ethanol (10, 14, and 18%). Following the self-administration testing, RIIbeta(+/+) and RIIbeta(-/-) mice were given access to 2 bottles, one containing water and the other ethanol to replicate the voluntary ethanol drinking data previously from our laboratory. Finally, immediately after voluntary consumption all mice were again tested for self-administration of 10% ethanol. Alterations in the reinforcement schedule were also explored as RIIbeta(+/+) and RIIbeta(-/-) mice were tested for self-administration of 10% ethanol at FR-3 and FR-5 schedules. RESULTS: The RIIbeta(-/-) mice displayed lower operant responding for ethanol and food reinforcement compared with RIIbeta(+/+) controls. However, this effect was driven by a significant increase in lever responses made by female RIIbeta(+/+) mice. When the excessive lever responses of the female RIIbeta(+/+) mice are accounted for, the RIIbeta(-/-) mice show ethanol lever responses comparable to controls. Following operant self-administration testing, RIIbeta(-/-) mice of both sexes consumed more ethanol solution compared with RIIbeta(+/+) mice during 2-bottle testing. CONCLUSIONS: Increased ingestion of ethanol by RIIbeta(-/-) mice is likely the result of altered PKA activity within neuronal pathways that control ethanol-consummatory behaviors. Conversely, the RIIbeta subunit of PKA appears not to play a critical role in neuronal pathways that regulate appetitive behaviors directed at obtaining ethanol. Finally, increased operant self-administration of food and ethanol by female wild-type mice was absent in female RIIbeta(-/-) mice, suggesting that normal PKA signaling may be part of a general, and sex-dependent, mechanism involved with reinforcement-seeking behavior.     

Changes in activity and regulation of the cardiac Ca2+ channel (L-type) by protein kinase C in chronic alcohol-exposed rats

Background: It has been reported recently that long‐term alcohol exposure in rats increases the number of dihydropyridine binding sites in cardiac membrane preparations. We fed Sprague Dawley® rats a liquid diet that contained ethanol as 36% of total calories for 4 to 6 months and studied how alcohol exposure affected the activity and regulation of the cardiac Ca²⁺ channel. Methods: Dihydropyridine‐sensitive cardiac Ca²⁺ channel activity was measured as the rate of Mn²⁺ quench of the cytosolic fura‐2 signal in electrically stimulated myocytes. Results: In control rat myocytes, pretreatment with phorbol 12‐myristate 13‐acetate (PMA), an activator of protein kinase C (PKC), reduced the rate of Mn²⁺ quench to 68% of the untreated cell response. Pretreatment with GF109203X, a protein kinase C inhibitor, enhanced the rate of influx by 56%, whereas Gö6976, an inhibitor of PKC α, β, and γ, did not affect the rate of influx. By contrast, PMA did not affect the rate of Mn²⁺ quench in alcoholic myocytes; however, the PKC inhibitor GF109203X still enhanced the rate of Mn²⁺ quench by 33%. Similar to control myocytes, no effect was observed after pretreatment with Gö6976 in the alcoholic cells. In both Western blot and immunoprecipitation experiments, PKC ? expression in alcohol‐exposed myocytes was reduced to 68% of the control. However, the ratio of membrane/cytosolic distribution of PKC ? in alcoholic myocytes was increased from 1.6 to 2.6. No change was detected in the expression of PKC α and PKC δ. PKC activity, measured in the presence of Gö6976, which inhibits PKC α, β, and γ, was reduced in alcoholic myocytes to 57% of the control, but the proportion of PKC activity in the particulate fraction was increased from 26% in the control myocytes to 36% in the alcoholic myocytes. Conclusions: Altered expression and activity of PKC may be associated with changes in the regulation of the cardiac Ca²⁺ channel found in the hearts of rats chronically exposed to alcohol. Specifically, we found that the novel class of PKC isozymes is responsible for regulating the cardiac Ca²⁺ channel in control cardiomyocytes, and that the loss of PMA modulation found in the alcoholic cells may be due, in part, to reduced expression and altered distribution of PKC ?.     

Chronic exposure to high glucose impairs bradykinin-stimulated nitric oxide production by interfering with the phospholipase-C-implicated signalling pathway in endothelial cells: evidence for the involvement of protein kinase C

Aims/hypothesis Overwhelming evidence indicates that endothelial cell dysfunction in diabetes is characterised by diminished endothelium-dependent relaxation, but the matter of the underlying molecular mechanism remains unclear. As nitric oxide (NO) production from the endothelium is the major player in endothelium-mediated vascular relaxation, we investigated the effects of high glucose on NO production, and the possible alterations of signalling pathways implicated in this scenario.Methods NO production and intracellular Ca²⁺ levels ([Ca²⁺]_i) were assessed using the fluorescent probes 4,5-diaminofluorescein diacetate and fura-2 respectively.Results Exposure of cultured bovine aortic endothelial cells to high glucose for 5 or 10 days significantly reduced NO production induced by bradykinin (but not by Ca²⁺ ionophore) in a time- and dose-dependent manner. This was probably due to an attenuation in bradykinin-induced elevations of [Ca²⁺]_i under these conditions, since a close correlation between [Ca²⁺]_i increases and NO generation was observed in intact bovine aortic endothelial cells. Both bradykinin-promoted intracellular Ca²⁺ mobilisation and extracellular Ca²⁺ entry were affected. Moreover, bradykinin-induced formation of Ins(1,4,5)P₃, a phospholipase C product leading to increases in [Ca²⁺]_i, was also inhibited following high glucose culture. This abnormality was not attributable to a decrease in inositol phospholipids, but possibly to a reduction in the number of bradykinin receptors. The alterations in NO production, the increases in [Ca²⁺]_i, and the bradykinin receptor number due to high glucose could be largely reversed by protein kinase C inhibitors and d--tocopherol (antioxidant).Conclusions/interpretation Chronic exposure to high glucose reduces NO generation in endothelial cells, probably by impairing phospholipase-C-mediated Ca²⁺ signalling due to excess protein kinase C activation. This defect in NO release may contribute to the diminished endothelium-dependent relaxation and thus to the development of cardiovascular diseases in diabetes.     

Possible involvement of protein kinase C activation in down-regulation of CD3 antigen on adult T cell leukaemia cells

Summary The role of protein kinase C (PKC) system on CD3 expression on adult T-cell leukaemia (ATL) was examined. The down-regulation of CD3 on ATL cells is reportedly induced by CD3 down-regulating factor (CD3DF) contained in serum and culture supernatants of leukaemia cells from acute type ATL patients. After we cultured normal PBMC with a PKC inhibitor, H-7, CD3DF activity for PBMC was reduced significantly. Culture with H-7 of HTLV-1 transformed T cells, ATL-2 cells whose CD3 expression had been decreased, led to enhancement of CD3 expression in a time-dependent manner. These findings suggest that CD3DF may play an important role as a PKC system activator, resulting in CD3 down-regulation.     

Effects of prenatal ethanol exposure on hypothalamic-pituitary-adrenal responses to chronic cold stress in rats

Animals prenatally exposed to ethanol typically exhibit hypothalamic-pituitary-adrenal (HPA) hyperresponsiveness to stressors. In contrast to previous studies that have investigated effects of prenatal ethanol exposure on HPA responses to acute or intermittent stressors, our study investigated HPA responses to a chronic continuous stressor, cold stress (4 degrees C for 0, 1, or 3 days). We tested the hypothesis that prenatal ethanol exposure would result in increased plasma corticosterone (CORT) and adrenocorticotropin (ACTH) responses and increased peptide [corticotropin-releasing factor and vasopressin] mRNA levels in the paraventricular nucleus (PVN) of the hypothalamus compared to that in control animals. In addition, CORT and ACTH responses were measured after exposure to an acute stressor (i.p. isotonic saline injection), superimposed during chronic cold exposure, to examine possible sensitization of the HPA response to the acute stress. Thus, blood samples were collected at the end of each of the three periods of cold exposure, either before (0 min) or 15 min after acute stress. The subjects were adult male and female Sprague-Dawley rat offspring from prenatal ethanol (E), pair-fed (PF), and ad libitum-fed control (C) treatment groups. Exposure to cold stress resulted in significant body weight loss in E males at 1 day and in both males and females of all prenatal treatment groups by 3 days of cold stress. Males in all prenatal groups also exhibited significant increases in adrenal weight:body weight ratios. Cold stress alone (0 min condition) increased CORT levels in E males and overall ACTH levels in E males and females compared to controls. ACTH levels were also higher overall in E compared to control males after acute stress (15 min condition). Sensitization of the CORT response to acute stress was observed in males but not females across all prenatal treatment groups. Corticotropin-releasing factor and vasopressin mRNA levels in the PVN were not significantly affected by prenatal treatment or chronic cold stress in either males or females. In contrast, both males and females displayed increases in PVN thyrotropin-releasing hormone (TRH) mRNA levels after cold stress. These data support and extend previous work demonstrating differential effects of prenatal ethanol exposure on HPA responsiveness of male and female offspring, and suggest that E males may be more vulnerable to the effects of chronic cold stress than E females.     

阻断肾素-血管紧张素系统对糖尿病大鼠肾脏蛋白激酶C活性的影响

目的　观察阻断肾素 血管紧张素系统对糖尿病大鼠肾组织蛋白激酶C(PKC)活性的影响。方法　以链脲佐菌素造成大鼠糖尿病模型。未给予链脲佐菌素的大鼠作为正常对照组 (A组 ) ,糖尿病大鼠分为未处理组 (B组 )、福辛普利治疗组 (C组 )、洛沙坦治疗组 (D组 )和福辛普利 洛沙坦联合治疗组 (E组 )。 2 4周后测血糖、HbA1c、肾重 /体重、尿蛋白排泄率 (UPER)及肾组织PKC活性。结果　 ( 1)B组的肾重 /体重和UPER显著高于其余各组 ,C组和D组之间差异无显著性 ,E组较C组和D组更低 (P <0 .0 5 )。 ( 2 )B组肾组织膜PKC活性显著高于A组 (P <0 .0 0 1)、C组、D组和E组 (P <0 .0 1) ;B组胞液PKC活性显著低于A组(P <0 .0 1)、C组、D组和E组 (P <0 .0 5 ) ;B组胞液和膜PKC活性比显著低于A组 (P <0 .0 0 1)、C组、D组和E组 (P <0 .0 1)。C组和D组胞液PKC活性、膜PKC活性及二者之比差异无显著性 ,但E组的变化较C组和D组更为显著 (P <0 .0 5 )。结论　 ( 1)血管紧张素转化酶抑制剂 (ACEI)和血管紧张素Ⅱ受体拮抗剂(ARB)均能减轻糖尿病大鼠的肾脏肥大 ,减少UPER。 ( 2 )长期高糖可引起大鼠肾脏PKC活性异常升高并诱导胞液PKC向细胞膜转位。 ( 3 )ACEI和ARB均可抑制糖尿病大鼠肾脏PKC活性的升高及转位 ,二者的作用相当 ,联合     

Evidence for the participation of protein kinase C and 3′,5′-cyclic AMP-dependent protein kinase in the stimulation of muscle cell proliferation by 1,25-dihydroxy-vitamin D3

Treatment with 1,25-dihydroxy-vitamin D₃ (1,25(OH)₂D₃) (1–12 h, 10⁻¹⁰ M) stimulates DNA synthesis in proliferating myoblasts, with an early response at 2–4 h of treatment followed by a maximal effect at 10 h. To investigate the mechanism involved in the mitogenic action of the hormone we studied the possible activation of intracellular messengers by 1,25(OH)₂D₃. The initial phase of stimulation of [³H]thymidine incorporation into DNA by the sterol was mimicked by the protein kinase C activator tetradecanoylphorbol acetate (TPA) in a manner which was dose dependent and specific as the inactive analog 4-phorbol was without effect. Maximal responses to TPA (100 nM) were obtained at 4 h. Staurosporine, a protein kinase C inhibitor, blocked the effect of 1,25(OH)₂D₃ on myoblast proliferation at 4 h. In addition, a fast (1–5 min) elevation of diacylglycerol levels and membrane-associated protein kinase C activity was observed in response to 1,25(OH)₂D₃. The adenylate cyclase activator forskolin (20 μM) and dibutyryl-cAMP (50 μM) increased DNA synthesis reproducing the second 1,25(OH)₂D₃-dependent stimulatory phase at 10 h. Inhibitors of protein kinase A blocked the increase in muscle cell DNA synthesis induced by 1,25(OH)₂D₃ at 10 h. Significant increases in cyclic AMP levels were detected in myoblasts treated with the sterol for 1–10 h. The calcium channel antagonist nifedipine (5–10 μM) abolished both the effects of 4-h treatment with 1,25(OH)₂D₃ or TPA and 10-h treatment with 1,25(OH)₂D₃ or dibutyryl-cAMP. Similar to the calcium channel agonist Bay K8644, 1,25(OH)₂D₃ stimulated myoblast ⁴⁵Ca uptake and its effects were blocked by nifedipine. Our results suggest that activation of calcium channels by phosphorylation via protein kinases C and A and is involved in the mitotic response of myoblasts to 1,25(OH)₂D₃.     

Effects of early postnatal exposure to ethanol on retinal ganglion cell morphology and numbers of neurons in the dorsolateral geniculate in mice

Background: The adverse effects of fetal and early postnatal ethanol intoxication on peripheral organs and the central nervous system are well documented. Ocular defects have also been reported in about 90% of children with fetal alcohol syndrome, including microphthalmia, loss of neurons in the retinal ganglion cell (RGC) layer, optic nerve hypoplasia, and dysmyelination. However, little is known about perinatal ethanol effects on retinal cell morphology. Examination of the potential toxic effects of alcohol on the neuron architecture is important because the changes in dendritic geometry and synapse distribution directly affect the organization and functions of neural circuits. Thus, in the present study, estimations of the numbers of neurons in the ganglion cell layer and dorsolateral geniculate nucleus (dLGN), and a detailed analysis of RGC morphology were carried out in transgenic mice exposed to ethanol during the early postnatal period. Methods: The study was carried out in male and female transgenic mice expressing yellow fluorescent protein (YFP) controlled by a Thy‐1 (thymus cell antigen 1) regulator on a C57 background. Ethanol (3 g/kg/d) was administered to mouse pups by intragastric intubation throughout postnatal days (PDs) 3 to 20. Intubation control (IC) and untreated control (C) groups were included. Blood alcohol concentration was measured in separate groups of pups on PDs 3, 10, and 20 at 4 different time points, 1, 1.5, 2, and 3 hours after the second intubation. Numbers of neurons in the ganglion cell layer and in the dLGN were quantified on PD20 using unbiased stereological procedures. RGC morphology was imaged by confocal microscopy and analyzed using Neurolucida software. Results: Binge‐like ethanol exposure in mice during the early postnatal period from PDs 3 to 20 altered RGC morphology and resulted in a significant decrease in the numbers of neurons in the ganglion cell layer and in the dLGN. In the alcohol exposure group, out of 13 morphological parameters examined in RGCs, soma area was significantly reduced and dendritic tortuosity significantly increased. After neonatal exposure to ethanol, a decrease in total dendritic field area and an increase in the mean branch angle were also observed. Interestingly, RGC dendrite elongation and a decrease in the spine density were observed in the IC group, as compared to both ethanol‐exposed and pure control subjects. There were no significant effects of alcohol exposure on total retinal area. Conclusions: Early postnatal ethanol exposure affects development of the visual system, reducing the numbers of neurons in the ganglion cell layer and in the dLGN, and altering RGCs’ morphology.     

脑死亡状态对巴马小型猪胰腺及小肠组织中蛋白激酶-C的影响

目的:探讨脑死亡状态下胰腺及小肠组织中蛋白激酶C(protein kinase C,PKC)水平的变化.方法:巴马小型猪10只,随机平均分为脑死亡组及对照组.用颅内加压法建立脑死亡模型,脑死亡后6,12和24 h点活检部分胰腺和小肠组织行电镜观察,并用RT-PCR和免疫组化法检测PKC-αmRNA和蛋白的表达情况.结果:脑死亡组胰腺和小肠组织中PKC-αmRNA均表达,并随着脑死亡时间的增加表达亮度增高,而在对照组胰腺和小肠组织中PKC-αmRNA无表达.脑死亡组PKC-α蛋白在胰腺和小肠组织中的表达显著高于对照组,并且6、12、24 h间也有显著差异(0.6209±0.031 vs 0.381±0.038 vs 0.151±0.0108;P<0.05).对照组PKC-α蛋白在胰腺及小肠细胞胞质内表达,仅见少量阳性细胞.电镜下,脑死亡组胰腺及小肠组织形态学变化明显重于对照组.结论:脑死亡状态下胰腺及小肠组织中PKC-αmRNA和蛋白表达水平明显升高,这可能与脑死亡状态下胰腺及小肠的组织损伤有关.     

雷公藤内酯醇对大鼠大脑皮质内注射β-淀粉样蛋白后补体C1q和C3表达的影响

目的 探讨雷公藤内酯醇对大鼠大脑皮质内注射β-淀粉样蛋白(Aβ)后补体C1q和C3表达的影响.方法 30只SD雄性大鼠随机等分成对照组、Aβ组、用药组.Aβ组大鼠给予双侧大脑皮质各一次性注射凝聚态Aβ1-40,对照组大鼠大脑皮质注射等量生理盐水,用药组大鼠在大脑皮质注射凝聚态Aβ1-40后腹腔注射雷公藤内酯醇,免疫组织化学染色和RT-PCR方法检测各组大鼠大脑皮质C1q和C3蛋白和mRNA的表达.结果 免疫组织化学染色显示,Aβ组大鼠大脑皮质C1q和C3免疫反应阳性细胞数和平均光密度明显高于对照组(P＜0.01);用药组大鼠大脑皮质C3免疫反应阳性细胞数较Aβ组明显减少(P<0.05),用药组大鼠大脑皮质C1q和C3免疫反应阳性细胞平均光密度较Aβ组明显减弱(P<0.01).RT-PCR结果显示,Aβ组大鼠大脑皮质C1q和C3 mRNA表达量明显高于对照组(P＜0.01);用药组大鼠大脑皮质C1q和C3 mRNA表达量明显低于Aβ组(P<0.05,P＜0.01).结论 雷公藤内酯醇对大鼠大脑皮质内注射Aβ后补体C1q和C3的表达有抑制作用.     

Effects of protein kinase C activation on cardiac repolarization and arrhythmogenesis in Langendorff-perfused rabbit hearts.

AIMS: Cardiac arrhythmias are still a major cause of mortality in western countries. Currently available antiarrhythmic drugs are limited by a low efficacy and proarrhythmic effects. The role of the protein kinase C (PKC) signalling pathway in arrhythmogenesis is still unclear. The goal of the present study was to test the effects of PKC stimulation on whole heart electrophysiology and its pro-/antiarrhythmic activity. METHODS AND RESULTS: Left ventricular (LV) action potential duration (APD 90%) was determined in 27 Langendorff-perfused rabbit hearts, using Tyrode solution plus the PKC agonist phorbol-12-myristate-13-acetate (PMA; 100 nM) alone (nine rabbits), Verapamil alone (n = 6), or PMA in combination with Verapamil (0.25 mg/L, six rabbits), or bisindolylmaleimide (0.5 microM, n = 6). Intermittent programmed extra-stimulation was performed to induce ventricular arrhythmias. Administration of PMA alone led to a significant shortening of repolarization (APD 90%, 157 +/- 8 vs. 128 +/- 5 ms, P<0.05). Non-sustained ventricular fibrillation (VF) could be induced in seven out of nine animals. After perfusion of Verapamil (156 +/- 6 vs. 169 +/- 4 ms, P>0.05) or bisindolylmaleimide, a selective inhibitor of PKC (136 +/- 4 vs. 146 +/- 4 ms, P>0.05), PMA-induced shortening of repolarization could be inhibited, and induction of VF failed. Verapamil alone did not affect APD and VF could not be induced. CONCLUSIONS: Activation of PKC facilitates induction of VF, which is most likely due to a shortening of repolarization and a prominent calcium influx. These findings demonstrate involvement of the PKC-signalling pathway in arrhythmogenesis.     

洛沙坦对蛋白激酶C在慢性缺氧大鼠模型肺动脉胶原表达作用的影响

目的　观察洛沙坦对蛋白激酶C(PKC)在慢性缺氧大鼠模型肺动脉胶原表达作用的影响。方法　将二级SD大鼠分为 3组 :A组 (正常对照组 )大鼠室内常规饲养。B组 (单纯缺氧 4周组 )大鼠置于常压低氧舱中 ,舱内充入氮气 ,使氧浓度维持在 (1 0 0± 0 5) % ,每天 8h ,每周 6d ,连续 4周 ;大鼠每天缺氧前用 2ml蒸馏水灌胃。C组 (洛沙坦干预组 )缺氧条件同B组 ,大鼠每天缺氧前用洛沙坦 (洛沙坦 50mg/kg溶于 2ml蒸馏水 )灌胃。采用透射电镜、放射活性测定法、免疫组化、原位杂交等方法观察 3组大鼠肺细小动脉超微结构、肺组织PKC活性、肺动脉管壁PKC免疫组化及Ⅰ、Ⅲ型胶原和Ⅰ、Ⅲ型前胶原基因表达的变化。结果　 (1 )B组大鼠平均肺动脉压、右心室重量比显著高于A组(P <0 0 1 ) ,C组显著低于B组 (P <0 0 1 )。 (2 )光镜下可见B组大鼠肺血管管壁厚度占血管外经的百分比、管壁面积占管总面积的百分比显著高于A组 (P <0 0 1 ) ,C组显著低于B组 (P <0 0 1 )。电镜下可见B组大鼠肺动脉胶原纤维较A组明显为多 ,C组较B组明显为少。 (3)B组大鼠肺组织细胞PKC总活性、胞膜PKC活性、胞质PKC活性及胞膜PKC活性占PKC总活性的百分比显著高于A组(P <0 0 1 ) ,C组上述指标均显著低于B组 (P <0 0 1 )。 (4)免疫组化显示 ,B     

缺血后处理对心肌缺血再灌注大鼠心肌梗死面积和细胞蛋白激酶Cα表达的影响

目的 研究心肌缺血后处理对老年大鼠急性心肌缺血再灌注损伤后心肌梗死面积、心肌细胞蛋白激酶Cα(PKCα)表达的影响,并探讨其可能机制.方法 120只健康雄性Wistar大鼠,根据鼠龄分为老年和成年组,每组再分为对照组(缺血30 min再灌注3 h,12只)和5 s、10 s、30 s、60 s组(缺血30 min,再灌注开始时分别给予5 s、10 s、30 s、60 s再通-闭塞冠状动脉处理后再灌注共3 h,每组12只).2,3,5-三苯基氯化四氮唑染色测定心肌梗死面积,免疫组化技术检测心肌细胞PKCα表达.结果 不同时间缺血处理心肌梗死面积和PKCα表达不同,对照组、10 s和30 s再通-闭塞处理均可缩小老年和成年大鼠心肌梗死面积[分别为(55.9±6.0)%和(47.4±5.5)%、(48.1±5.3)%、和(39.2±5.7)%、(48.8±6.8)%和(40.2±6.1)%],PKCα表达增加(均P<0.05);老年5 s组再通-闭塞处理可增加大鼠心肌梗死面积,老年5 s组梗死面积为(63.5±5.4)%,PKCα表达降低(均P<0.05).结论 缺血后处理对老年大鼠急性心肌缺血再灌注损伤具有保护作用;缺血后处理效果与再通-闭塞时间有关.     

Effects of withdrawal from chronic intermittent ethanol vapor on the level and circadian periodicity of running-wheel activity in C57BL/6J and C3H/HeJ mice

Background: Alcohol withdrawal is associated with behavioral and chronobiological disturbances that may persist during protracted abstinence. We previously reported that C57BL/6J (B6) mice show marked but temporary reductions in running‐wheel activity, and normal free‐running circadian rhythms, following a 4‐day chronic intermittent ethanol (CIE) vapor exposure (16 hours of ethanol vapor exposure alternating with 8 hours of withdrawal). In the present experiments, we extend these observations in 2 ways: (i) by examining post‐CIE locomotor activity in C3H/HeJ (C3H) mice, an inbred strain characterized by high sensitivity to ethanol withdrawal, and (ii) by directly comparing the responses of B6 and C3H mice to a longer‐duration CIE protocol. Methods: In Experiment 1, C3H mice were exposed to the same 4‐day CIE protocol used in our previous study with B6 mice (referred to here as the 1‐cycle CIE protocol). In Experiment 2, C3H and B6 mice were exposed to 3 successive 4‐day CIE cycles, each separated by 2 days of withdrawal (the 3‐cycle CIE protocol). Running‐wheel activity was monitored prior to and following CIE, and post‐CIE activity was recorded in constant darkness to allow assessment of free‐running circadian period and phase. Results: C3H mice displayed pronounced reductions in running‐wheel activity that persisted for the duration of the recording period (up to 30 days) following both 1‐cycle (Experiment 1) and 3‐cycle (Experiment 2) CIE protocols. In contrast, B6 mice showed reductions in locomotor activity that persisted for about 1 week following the 3‐cycle CIE protocol, similar to the results of our previous study using a 1‐cycle protocol in this strain. Additionally, C3H mice showed significant shortening of free‐running period following the 3‐cycle, but not the 1‐cycle, CIE protocol, while B6 mice showed normal free‐running rhythms. Conclusions: These results reveal genetic differences in the persistence of ethanol withdrawal‐induced hypo‐locomotion. In addition, chronobiological alterations during extended abstinence may depend on both genetic susceptibility and an extended prior withdrawal history. The present data establish a novel experimental model for long‐term behavioral and circadian disruptions associated with ethanol withdrawal.