Cannabinoids modulate the P-type high-voltage-activated calcium currents in purkinje neurons

Endocannabinoids released by postsynaptic cells inhibit neurotransmitter release in many central synapses by activating presynaptic cannabinoid CB1 receptors. In particular, in the cerebellum, endocannabinoids inhibit synaptic transmission at granule cell to Purkinje cell synapses by modulating presynaptic calcium influx via N-, P/Q-, and R-type calcium channels. Using whole cell patch-clamp techniques, we show that in addition to this presynaptic action, both synthetic and endogenous cannabinoids inhibit P-type calcium currents in isolated rat Purkinje neurons independent of CB1 receptor activation. The IC50 for the anandamide (AEA)-induced inhibition of P-current peak amplitude was 1.04 +/- 0.04 microM. In addition, we demonstrate that all the tested cannabinoids in a physiologically relevant range of concentrations strongly accelerate inactivation of P currents. The effects of AEA cannot be attributed to the metabolism of AEA because a nonhydrolyzing analogue of AEA, methanandamide inhibited P-type currents with a similar efficacy. All effects of cannabinoids on P-type Ca2+ currents were insensitive to antagonists of CB1 cannabinoid or vanilloid TRPV1 receptors. In cerebellar slices, WIN 55,212-2 significantly affected spontaneous firing of Purkinje neurons in the presence of CB1 receptor antagonist, in a manner similar to that of a specific P-type channel antagonist, indicating a possible functional implication of the direct effects of cannabinoids on P current. Taken together these findings demonstrate a functionally important direct action of cannabinoids on P-type calcium currents.     

Endocannabinoids facilitate the induction of LTP in the hippocampus

Exogenous cannabinoids disrupt behavioral learning and impede induction of long-term potentiation (LTP) in the hippocampus, yet endogenous cannabinoids (endocannabinoids) transiently suppress inhibitory post-synaptic currents (IPSCs) by activating cannabinoid CB1 receptors on GABAergic interneurons. We found that release of endocannabinoids by a rat CA1 pyramidal cell during this depolarization-induced suppression of inhibition (DSI) enabled a normally ineffective train of excitatory post-synaptic currents (EPSCs) to induce LTP in that cell, but not in neighboring cells. By showing that endocannabinoids facilitate LTP induction and help target LTP to single cells, these data shed new light on the physiological roles of endocannabinoids and may lead to a greater understanding of their effects on behavior and potential clinical use.     

Tumor necrosis factor-related apoptosis-inducing ligand can induce apoptosis in subsets of premalignant cells

During the transformation from a normal to a malignant cell, several mutations are required to bypass the pathways responsible for controlling proliferation. Premalignant cells have acquired some, but not all of these mutations and consequently have not yet attained a malignant phenotype characterized by tumor formation in vivo. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in malignant cells while sparing normal ones and is currently being considered as adjuvant therapy for various human malignancies. Whether TRAIL is effective in inducing apoptosis in premalignant cells is unclear, however. We studied the effect of TRAIL on two human premalignant cell lines the SV7tert and HA1E cells. Both cell lines had been immortalized by the addition of simian virus 40 large T antigen and the telomerase subunit hTERT, but had not been transformed into malignant cells. TRAIL initiated apoptosis by activating both the mitochondrial-independent and -dependent apoptotic pathways in both cell lines at relatively low doses whereas it had no effect on normal human pulmonary artery smooth muscle cells even at high doses. These results suggest that TRAIL can induce apoptosis in premalignant cells and suggests a novel therapy for the treatment of premalignant lesions in vivo.     

Mode of action of cannabinoids on nociceptive nerve endings

In recent years, cannabinoids have emerged as attractive alternatives or supplements to therapy for chronic pain states. However, in humans the activation of cannabinoid receptors in neurons of the central nervous system is associated with psychotropic side effects, temporary memory impairment and dependence, which arise via the effects of cannabinoids on forebrain circuits. For clinical exploitation of the analgesic properties of cannabinoids, a major challenge is to devise strategies that reduce or abolish their adverse effects on cognitive, affective and motor functions without attenuating their analgesic effects. The cannabinoid receptor family currently includes two cloned metabotropic receptors: CB1, CB2 and possibly GPR55 which are distributed widely across many key loci in pain-modulating pathways, including the peripheral terminals of primary afferents. Modulation of transducer ion channels expressed at nociceptive terminals occurs upon activation of metabotropic cannabinoid receptors, but direct cannabinoid action on ion channels involved in sensory transduction or regulation of neuron excitability likely contributes to the peripheral cannabinoid effects.     

Cardiovascular actions of cannabinoids and their generation during shock

Marijuana is a widely abused recreational drug well known for its psychoactive properties. Cannabinoids, the active ingredients of marijuana, elicit their neurobehavioral effects by interacting with the CB₁ cannabinoid receptor subtype, expressed primarily in the brain but also present in some peripheral tissues. A second receptor subtype, the CB₂ receptor, is expressed on cells of the immune system and is thought to be responsible for the immunosuppressant effects of cannabinoids. Recently, endogenous lipidlike substances have been identified, including arachidonyl ethanolamide (anandamide) and 2-arachidonyl glyceride, that bind to cannabinoid receptors and mimic many of the neurobehavioral effects of plant-derived cannabinoids. Both plant-derived cannabinoids and the endogenous ligands have been shown to elicit hypotension and bradycardia via activation of peripherally located CB₁ receptors. Possible underlying mechanisms include presynaptic CB₁ receptor mediated inhibition of norepinephrine release from peripheral sympathetic nerve terminals, and/or direct vasodilation via activation of vascular cannabinoid receptors. The latter may also be the target of endocannabinoids of vascular endothelial origin. Recent studies indicate that a peripheral endogenous cannabinoid system in circulating macrophages and platelets is activated in hemorrhagic and septic shock and may contribute to the hypotension associated with these conditions via activation of vascular cannabinoid receptors. The potential role of this mechanism in human shock conditions is under investigation. Received: 20 May 1998 / Accepted: 24 August 1998     

Cannabinoid agonist, CP 55,940, prevents capsaicin-induced sensitization of spinal cord dorsal horn neurons

Low doses of cannabinoids applied intrathecally attenuate capsaicin-evoked heat and mechanical hyperalgesia via CB1 receptors. Although cannabinoids produce antinociception, in part, by attenuating responses of nociceptive neurons in the spinal cord, few studies have examined the effect of cannabinoids on sensitization of spinal neurons. We therefore investigated whether a cannabinoid receptor agonist, CP 55,940, attenuated excitation and sensitization of spinal nociceptive neurons produced by intraplantar injection of 0.1% capsaicin (10 microl). In rats, wide-dynamic-range (WDR) and high-threshold (HT) neurons were classified according to responses evoked by mechanical stimuli of varying intensity. CP 55,940 (10 microg in 50 microl) or vehicle was applied directly to the spinal cord and responses to mechanical (von Frey monofilament) and heat stimuli were recorded 10 min after drug treatment. CP 55,940 alone did not alter responses to mechanical stimuli; however the enhanced responses to mechanical stimuli after injection of capsaicin into the receptive field were dose dependently attenuated in both HT and WDR neurons. Vehicle-treated neurons increased their response to 300.6 +/- 52.1% of baseline after capsaicin, whereas CP 55,940-treated neurons responded at 153.0 +/- 27.1% of baseline. The effects of CP 55,940 on sensitization to heat were less pronounced; however, CP 55,940 attenuated the capsaicin-evoked decrease in heat threshold in HT neurons. The attenuation by CP 55,940 of sensitization to mechanical stimuli was blocked by pretreatment of the spinal cord with the CB1 receptor antagonist, SR141716A. These studies demonstrate that cannabinoid application to the spinal cord prevents central sensitization.     

Mechanisms of cannabinoid-receptor-mediated inhibition of synaptic transmission in cultured hippocampal pyramidal neurons.

Cannabinoids, such as marijuana, are known to impair learning and memory perhaps through their actions in the hippocampus where cannabinoid receptors are expressed at high density. Although cannabinoid receptor activation decreases glutamatergic synaptic transmission in cultured hippocampal neurons, the mechanisms of this action are not known. Cannabinoid receptor activation also inhibits calcium channels that support neurotransmitter release in these cells, making modulation of these channels a candidate for cannabinoid-receptor-mediated effects on synaptic transmission. Whole cell patch-clamp recordings of glutamatergic neurons cultured from the CA1 and CA3 regions of the hippocampus were used to identify the mechanisms of the effects of cannabinoids on synaptic transmission. Cannabinoid receptor activation reduced excitatory postsynaptic current (EPSC) size by approximately 50% but had no effect on the amplitude of spontaneous miniature EPSCs (mEPSCs). This reduction in EPSC size was accompanied by an increase in paired-pulse facilitation measured in low (1 mM) extracellular calcium and by a decrease in paired-pulse depression measured in normal (2.5 mM) extracellular calcium. Together, these results strongly support the hypothesis that cannabinoid receptor activation decreases EPSC size by reducing release of neurotransmitter presynaptically while having no effect on postsynaptic sensitivity to glutamate. Further experiments were done to identify the molecular mechanisms underlying this cannabinoid-receptor-mediated decrease in neurotransmitter release. Cannabinoid receptor activation had no effect on the size of the presynaptic pool of readily releasable neurotransmitter-filled vesicles, eliminating reduction in pool size as a mechanism for cannabinoid-receptor-mediated effects. After blockade of Q- and N-type calcium channels with omega-agatoxin TK and omega-conotoxin GVIA; however, activation of cannabinoid receptors reduced EPSC size by only 14%. These results indicate that cannabinoid receptor activation reduces the probability that neurotransmitter will be released in response to an action potential via an inhibition of presynaptic Q- and N-type calcium channels. This molecular mechanism most likely contributes to the impairment of learning and memory produced by cannabinoids and may participate in the analgesic, antiemetic, and anticonvulsive effects of these drugs as well.     

丹参酮Ⅱa对急性髓系白血病NB4细胞增殖和凋亡的影响及其机制

目的观察丹参酮Ⅱa对急性髓系白血病细胞增殖和凋亡的影响,并初步分析其作用机制.方法人急性髓系白血病细胞NB4分别用不同浓度的丹参酮Ⅱa处理,11.2μmol/L柔红霉素作为阳性对照,未给予药物作为阴性对照.观察NB4细胞增殖、细胞周期、凋亡及相关通路蛋白的变化.结果丹参酮Ⅱa可明显抑制NB4细胞增殖,诱导细胞周期发生G1期阻滞,促进其凋亡,具有浓度依赖性(P<0.05).丹参酮Ⅱa可剂量性下调p-PI3K/PI3K、p-AKT/AKT及m-TOR的表达(P<0.05).结论丹参酮Ⅱa可抑制NB4细胞增殖,诱导细胞周期发生G1期阻滞,促进其凋亡,可能与抑制PI3K/AKT/m-TOR信号通路有关.     

Cannabinoid suppression of noxious heat-evoked activity in wide dynamic range neurons in the lumbar dorsal horn of the rat

The effects of cannabinoid agonists on noxious heat-evoked firing of 62 spinal wide dynamic range (WDR) neurons were examined in urethan-anesthetized rats (1 cell/animal). Noxious thermal stimulation was applied with a Peltier device to the receptive fields in the ipsilateral hindpaw of isolated WDR neurons. To assess the site of action, cannabinoids were administered systemically in intact and spinally transected rats and intraventricularly. Both the aminoalkylindole cannabinoid WIN55,212-2 (125 microg/kg iv) and the bicyclic cannabinoid CP55,940 (125 microg/kg iv) suppressed noxious heat-evoked activity. Responses evoked by mild pressure in nonnociceptive neurons were not altered by CP55,940 (125 microg/kg iv), consistent with previous observations with another cannabinoid agonist, WIN55,212-2. The cannabinoid induced-suppression of noxious heat-evoked activity was blocked by pretreatment with SR141716A (1 mg/kg iv), a competitive antagonist for central cannabinoid CB1 receptors. By contrast, intravenous administration of either vehicle or the receptor-inactive enantiomer WIN55,212-3 (125 microg/kg) failed to alter noxious heat-evoked activity. The suppression of noxious heat-evoked activity induced by WIN55,212-2 in the lumbar dorsal horn of intact animals was markedly attenuated in spinal rats. Moreover, intraventricular administration of WIN55,212-2 suppressed noxious heat-evoked activity in spinal WDR neurons. By contrast, both vehicle and enantiomer were inactive. These findings suggest that cannabinoids selectively modulate the activity of nociceptive neurons in the spinal dorsal horn by actions at CB1 receptors. This modulation represents a suppression of pain neurotransmission because the inhibitory effects are selective for pain-sensitive neurons and are observed with different modalities of noxious stimulation. The data also provide converging lines of evidence for a role for descending antinociceptive mechanisms in cannabinoid modulation of spinal nociceptive processing.     

The agonists for nociceptors are ubiquitous, but the modulators are specific: P2X receptors in the sensory neurons are modulated by cannabinoids

P2X2 and P2X3 receptors expressed in mammalian sensory neurons participate in nociception. Cannabinoid receptors modulate nociceptive processing in various models of pain. They are also expressed in nociceptive sensory neurons. We have examined the effect of cannabinoids on the slow P2X2 and P2X2/3 receptors in the cells isolated from nodosal and dorsal root ganglia of rat. The study was carried out by means of the whole-cell patch clamp and rapid superfusion methods. We have found that both endogenous and synthetic cannabinoids (anandamide, WIN55,212-2, and (R)-(+)-methanandamide) inhibit the slow response to ATP mediated by P2X2 and P2X2/3 receptors in a majority of tested neurons. This inhibition was significant but only partial: anandamide (0.5–1 μM) inhibited the response to 51±21% of control. In the remaining minority of tested neurons, the response was transiently facilitated. The effect of cannabinoids appears to be mediated via cannabinoid CB₁ receptors: it was reversibly inhibited by selective CB₁ antagonist, SR141716A (10 μM). Introduction of cyclic AMP (0.5 mM) into the cell potently facilitated the inhibitory effect of cannabinoids: the ATP-activated current was inhibited to 13±10% of control. These data indicate that cannabinoids may inhibit nociceptive responses produced by P2X receptors.     

Hypoxia-inducible factor-1alpha induces cell cycle arrest of endothelial cells

BACKGROUND: Hypoxia can induce tissue injury, including apoptosis of endothelial cells. However, little is known about the effects of hypoxia on endothelial cell function. We assessed the effects of hypoxia inducible factor (HIF)-1alpha on the functional characteristics of endothelial cells, particularly on cell cycle regulators, by cationic liposome-mediated transfection of HIF-1alpha-expression vector into the cells. RESULTS: Transfection of the HIF-1alpha gene in endothelial cells resulted in (a) reduced proliferation and detachment of the cells; (b) up-regulation of intracellular p21waf1/cip1 and down-regulation of bcl-2; (c) reduced activities of cyclin-dependent kinase (CDK)-4 and CDK-6; (d) cell cycle arrest at G0/G1 phase; and (e) apoptosis of the cells. CONCLUSIONS: HIF-1alpha can induce cell cycle arrest, resulting in the reduced proliferation and apoptosis of endothelial cells, and the hypoxia-induced cell death may be involved by suppression of anti-apoptotic molecule, bcl-2.     

Cannabinoid CB1 receptors are localized primarily on cholecystokinin-containing GABAergic interneurons in the rat hippocampal formation.

Localization of cannabinoid CB 1 receptors on GABAergic interneurons in the rat hippocampal formation was studied by double-labeling immunohistochemistry with confocal microscopy. Virtually all CB1-immunoreactive neurons (95%) are GABAergic. CB 1 fluorescence showed a punctate pattern. In contrast, the GABA fluorescence was distributed homogeneously, suggesting that while CB 1 receptors and GABA exist in the same cells they are not localized in the same subcellular compartments. Although virtually all CB1 neurons were GABAergic, many GABAergic neurons did not contain CB1 receptors. GABAergic interneurons in the hippocampal formation can be further divided into subpopulations with distinct connections and functions, using cell markers such as neuropeptides and calcium binding proteins. CB1 receptors were highly co-localized with cholecystokinin and partially co-localized with calretinin and calbindin, but not with parvalbumin. This suggests that cannabinoids may modulate GABAergic neurotransmission at the synapses on the soma and at synapses on the proximal dendrites of the principal neurons, as well as at synapses on other GABAergic interneurons.     

Apicidin, a novel histone deacetylase inhibitor, has profound anti-growth activity in human endometrial and ovarian cancer cells

Histone deacetylase inhibitors (HDACIs) can inhibit proliferation, induce cell cycle arrest and stimulate apoptosis of cancer cells. Our purpose was to investigate the antiproliferative effects of a novel HDACI, apicidin, on the Ishikawa endometrial cancer cell line, the SK-OV-3 ovarian cancer cell line and normal human endometrial epithelial cells. Endometrial and ovarian cancer cells were treated with various concentrations of apicidin, and the effects on cell growth, cell cycle, apoptosis and related measurements were investigated. MTT assays showed that all endometrial and ovarian cancer cell lines were sensitive to the growth inhibitory effect of apicidin, although normal endometrial epithelial cells were viable after the treatment with the same doses of apicidin that induced the growth inhibition of endometrial and ovarian cancer cells. Cell cycle analysis indicated that their exposure to apicidin decreased the proportion of cells in S-phase and increased the proportion in G0/G1 and/or G2/M phases of the cell cycle. Induction of apoptosis was confirmed by Annexin V staining of externalized phosphatidylserine and loss of the transmembrane potential of mitochondria. This induction occurred in concert with the altered expression of p21WAF1, p27KIP1, p16, cyclin A, and E-cadherin. Furthermore, apicidin treatment of these cell lines increased acetylation of H3 and H4 histone tails. These results suggest that apicidin exhibits the antiproliferative effects through selective induction of genes related to cell growth, malignant phenotype, and apoptosis. The findings raise the possibility that apicidin may prove particularly effective in the treatment of endometrial and ovarian cancers.     

The effects of cannabinoids on the brain.

Cannabinoids have a long history of consumption for recreational and medical reasons. The primary active constituent of the hemp plant Cannabis sativa is delta9-tetrahydrocannabinol (delta9-THC). In humans, psychoactive cannabinoids produce euphoria, enhancement of sensory perception, tachycardia, antinociception, difficulties in concentration and impairment of memory. The cognitive deficiencies seem to persist after withdrawal. The toxicity of marijuana has been underestimated for a long time, since recent findings revealed delta9-THC-induced cell death with shrinkage of neurons and DNA fragmentation in the hippocampus. The acute effects of cannabinoids as well as the development of tolerance are mediated by G protein-coupled cannabinoid receptors. The CB1 receptor and its splice variant CB1A, are found predominantly in the brain with highest densities in the hippocampus, cerebellum and striatum. The CB2 receptor is found predominantly in the spleen and in haemopoietic cells and has only 44% overall nucleotide sequence identity with the CB1 receptor. The existence of this receptor provided the molecular basis for the immunosuppressive actions of marijuana. The CB1 receptor mediates inhibition of adenylate cyclase, inhibition of N- and P/Q-type calcium channels, stimulation of potassium channels, and activation of mitogen-activated protein kinase. The CB2 receptor mediates inhibition of adenylate cyclase and activation of mitogen-activated protein kinase. The discovery of endogenous cannabinoid receptor ligands, anandamide (N-arachidonylethanolamine) and 2-arachidonylglycerol made the notion of a central cannabinoid neuromodulatory system plausible. Anandamide is released from neurons upon depolarization through a mechanism that requires calcium-dependent cleavage from a phospholipid precursor in neuronal membranes. The release of anandamide is followed by rapid uptake into the plasma and hydrolysis by fatty-acid amidohydrolase. The psychoactive cannabinoids increase the activity of dopaminergic neurons in the ventral tegmental area-mesolimbic pathway. Since these dopaminergic circuits are known to play a pivotal role in mediating the reinforcing (rewarding) effects of the most drugs of abuse, the enhanced dopaminergic drive elicited by the cannabinoids is thought to underlie the reinforcing and abuse properties of marijuana. Thus, cannabinoids share a final common neuronal action with other major drugs of abuse such as morphine, ethanol and nicotine in producing facilitation of the mesolimbic dopamine system.     

Differential effects of marijuana components on proliferation of spleen, lymph node and thymus cells in vitro

The effects of delta 9 THC and 11-OH THC on the proliferative response of murine spleen cells stimulated in vitro with the T cell mitogens Con A or PHA were compared with the effects of these drugs on the mitogen-induced proliferation of murine thymus and lymph node cells. Thymus cells were found to be suppressed at lower cannabinoid concentration than either spleen or lymph node cells. However, splenic cells were more easily suppressed than were the lymph node cells. Lymphoid cell numbers were varied from 1 X 10(6) to 8 X 10(6) cells and treated with a constant dose of either THC or 11-OH THC. When suppression was noted with spleen and lymph node cells, the smallest number of cells in the assay resulted in the greatest level of suppression of cell proliferation. No significant suppression to PHA induced proliferation was found for lymph node cells at any cell number tested. Thymus cells were always more readily suppressed than spleen or lymph node cells regardless of the number of cells in culture. Furthermore, 11-OH THC suppressed the responsiveness of the thymus cells to PHA more than to Con A under the experimental conditions used. Thus, the ability of cannabinoids to induce suppression of the proliferative response of lymphoid cells to mitogens depends on the organ source of the cells, nature of the cannabinoid (THC or 11-OH THC), dose of the cannabinoid, mitogen used (PHA or Con A), and number of cells in culture.(ABSTRACT TRUNCATED AT 250 WORDS)     

The neuronal distribution of cannabinoid receptor type 1 in the trigeminal ganglion of the rat

Cannabinoid compounds have been shown to produce antinociception and antihyperalgesia by acting upon cannabinoid receptors located in both the CNS and the periphery. A potential mechanism by which cannabinoids could inhibit nociception in the periphery is the activation of cannabinoid receptors located on one or more classes of primary nociceptive neurons. To address this hypothesis, we evaluated the neuronal distribution of cannabinoid receptor type 1 (CB1) in the trigeminal ganglion (TG) of the adult rat through combined in situ hybridization (ISH) and immunohistochemistry (IHC). CB1 receptor mRNA was localized mainly to medium and large diameter neurons of the maxillary and mandibular branches of the TG. Consistent with this distribution, in a de facto nociceptive sensory neuron population that exhibited vanilloid receptor type 1 immunoreactivity, colocalization with CB1 mRNA was also sparse (<5%). Furthermore, very few neurons (approximately 5%) in the peptidergic (defined as calcitonin gene-related peptide- or substance P-immunoreactive) or the isolectin B4-binding sensory neuron populations contained CB1 mRNA. In contrast, and consistent with the neuron-size distribution for CB1, nearly 75% of CB1-positive neurons exhibited N52-immunoreactivity, a marker of myelinated axons. These results indicate that in the rat TG, CB1 receptors are expressed predominantly in neurons that are not thought to subserve nociceptive neurotransmission in the noninjured animal. Taken together with the absence of an above background in situ signal for CB2 mRNA in TG neurons, these findings suggest that the peripherally mediated antinociceptive effects of cannabinoids may involve either as yet unidentified receptors or interaction with afferent neuron populations that normally subserve non-nociceptive functions.     

A novel histone deacetylase inhibitor, Scriptaid, induces growth inhibition, cell cycle arrest and apoptosis in human endometrial cancer and ovarian cancer cells

Histone deacetylase inhibitors (HDACIs) can inhibit cell proliferation, induce cell cycle arrest, and stimulate the apoptosis of cancer cells. We investigated the effects of a novel HDACI, Scriptaid, on the Ishikawa endometrial cancer cell line, SK-OV-3 ovarian cancer cell line, and normal human endometrial epithelial cells. Endometrial and ovarian cancer cells were treated with various concentrations of Scriptaid, and its effect on cell growth, cell cycle, apoptosis, and related measurements was investigated. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays showed that all endometrial and ovarian cancer cell lines were sensitive to the growth inhibitory effect of Scriptaid, although normal endometrial epithelial cells were viable after treatment with the same doses of Scriptaid that induced the growth inhibition of endometrial and ovarian cancer cells. Cell cycle analysis indicated that their exposure to Scriptaid decreased the proportion of cells in the S phase and increased the proportion in the G0/G1 and/or G2/M phases of the cell cycle. Induction of apoptosis was confirmed by annexin V staining of externalized phosphatidylserine and loss of the transmembrane potential of mitochondria. This induction occurred in concert with the altered expression of genes related to cell growth, malignant phenotype, and apoptosis. Furthermore, Scriptaid treatment of these cell lines increased acetylation of H3 and H4 histone tails. These results raise the possibility that Scriptaid may prove particularly effective in the treatment of endometrial and ovarian cancers.     

Cannabis and cannabinoids: pharmacology and rationale for clinical use

It is now known that there are at least two types of cannabinoid receptors. These are CB1 receptors, present mainly on central and peripheral neurones, and CB2 receptors, present mainly on immune cells. Endogenous cannabinoid receptor agonists ('endocannabinoids') have also been identified. The discovery of this 'endogenous cannabinoid system' has led to the development of selective CB1 and CB2 receptor ligands and fueled renewed interest in the clinical potential of cannabinoids. Two cannabinoid CB1 receptor agonists are already used clinically, as antiemetics or as appetite stimulants. These are D 9 - tetrahydrocannabinol (THC) and nabilone. Other possible uses for CB1 receptor agonists include the suppression of muscle spasm/spasticity associated with multiple sclerosis or spinal cord injury, the relief of chronic pain and the management of glaucoma and bronchial asthma. CB1 receptor antagonists may also have clinical applications, e. g. as appetite suppressants and in the management of schizophrenia or disorders of cognition and memory. So too may CB2 receptor ligands and drugs that activate cannabinoid receptors indirectly by augmenting endocannabinoid levels at cannabinoid receptors. When taken orally, THC seems to undergo variable absorption and to have a narrow 'therapeutic window' (dose range in which it is effective without producing significant unwanted effects). This makes it difficult to predict an oral dose that will be both effective and tolerable to a patient and indicates a need for better cannabinoid formulations and modes of administration. For the therapeutic potential of cannabis or CB1 receptor agonists to be fully exploited, it will be important to establish objectively and conclusively (a) whether these agents have efficacy against selected symptoms that is of clinical significance and, if so, whether the benefits outweigh the risks, (b) whether cannabis has therapeutic advantages over individual cannabinoids, (c) whether there is a need for additional drug treatments to manage any of the disorders against which cannabinoids are effective, and (d) whether it will be possible to develop drugs that have reduced psychotropic activity and yet retain the ability to act through CB1 receptors to produce their sought-after effects.     

X射线诱导Raji细胞凋亡的实验研究

目的探讨X射线对人Burkkit淋巴瘤细胞株Raji细胞增殖及凋亡的影响。方法用不同剂量X射线照射细胞,并在不同时间段用倒置显微镜观察照射后细胞的形态变化及生长抑制率,流式细胞仪检测细胞凋亡率、细胞周期,并观察X射线对克隆形成的影响。结果 16Gy照射后48h对Raji细胞的抑制率（92.67±1.20）%最显著;8Gy照射后48h早期凋亡率（42.04±3.62）%最高;8Gy照射后24h细胞周期G2/M期细胞（57.86±3.31）%,明显大于正常对照组（14.54±2.32）%;8Gy照射后第7天无克隆形成,第14天克隆数为（5.33±2.40）,明显小于正常对照组第7天（116.67±20.28）和第14天（263.33±20.27）。结论 X射线可抑制细胞增殖,并诱导细胞凋亡,照射后细胞周期阻滞在G2/M期,X射线8Gy照射后不能完全抑制Raji细胞的增殖。     

阿霉素对K562细胞凋亡及FAK mRNA的影响

目的探讨阿霉素体外作用于K562细胞后,观察其对细胞增殖的影响,促进细胞凋亡情况,以及调节细胞周期和粘着斑激酶（FAK）mRNA基因,进一步探讨通过调控FAK表达,研究抗白血病的作用机制。方法应用细胞增殖实验（CCK8法）观察不同浓度阿霉素作用不同时间对K562细胞增殖的影响,应用流式细胞仪观察不同浓度阿霉素对K562细胞细胞凋亡,细胞周期的影响,应用RT-PCR和Western blot技术检测不同浓度阿霉素作用对K562细胞36h后FAK mRNA以及蛋白表达水平的变化。结果随着阿霉素浓度增加及作用时间延长,K562细胞的增殖抑制率逐渐升高,同一时间不同浓度之间比较,或者同一浓度不同时间组之间比较,差异均有统计学意义（P〈0.05）;阿霉素能引起K562细胞凋亡,且随着药物浓度增加,凋亡率也逐渐增加,差异均有统计学意义（P〈0.05）;阿霉素能引起K562细胞周期阻滞,多停留在S期;阿霉素能引起K562细胞FAK mRNA表达显著降低。阿霉素能引起K562细胞FAK蛋白表达水平的降低。结论阿霉素抑制分裂期细胞的增殖,诱导细胞凋亡增加,对细胞FAK基因和蛋白水平均显著下调,为进一步研究FAK基因表达的调控与肿瘤细胞凋亡的分子机制提供了实验基础。