Possible involvement of the endocannabinoid system in the actions of three clinically used drugs

Cannabinoid Analgesia in Postoperative Pain Management: From Molecular Mechanisms to Clinical Reality

Postoperative pain (POP) is a challenging clinical phenomenon that affects the majority of surgical patients and demands effective management to mitigate adverse outcomes such as persistent pain. The primary goal of POP management is to alleviate suffering and facilitate a seamless return to normal function for the patient. Despite compelling evidence of its drawbacks, opioid analgesia remains the basis of POP treatment. Novel therapeutic approaches rely on multimodal analgesia, integrating different pharmacological strategies to optimize efficacy while minimizing adverse effects. The recognition of the imperative role of the endocannabinoid system in pain regulation has prompted the investigation of cannabinoid compounds as a new therapeutic avenue. Cannabinoids may serve as adjuvants, enhancing the analgesic effects of other drugs and potentially replacing or at least reducing the dependence on other long-term analgesics in pain management. This narrative review succinctly summarizes pertinent information on the molecular mechanisms, clinical therapeutic benefits, and considerations associated with the plausible use of various cannabinoid compounds in treating POP. According to the available evidence, cannabinoid compounds modulate specific molecular mechanisms intimately involved in POP. However, only two of the eleven clinical trials that evaluated the efficacy of different cannabinoid interventions showed positive results.

Arrestin Facilitates Rhodopsin Dephosphorylation in Vivo

Deactivation of G-protein-coupled receptors (GPCRs) involves multiple phosphorylations followed by arrestin binding, which uncouples the GPCR from G-protein activation. Some GPCRs, such as rhodopsin, are reused many times. Arrestin dissociation and GPCR dephosphorylation are key steps in the recycling process. In vitro evidence suggests that visual arrestin (ARR1) binding to light-activated, phosphorylated rhodopsin hinders dephosphorylation. Whether ARR1 binding also affects rhodopsin dephosphorylation in vivo is not known. We investigated this using both male and female mice lacking ARR1. Mice were exposed to bright light and placed in darkness for different periods of time, and differently phosphorylated species of rhodopsin were assayed by isoelectric focusing. For WT mice, rhodopsin dephosphorylation was nearly complete by 1 h in darkness. Surprisingly, we observed that, in the Arr1 KO rods, rhodopsin remained phosphorylated even after 3 h. Delayed dephosphorylation in Arr1 KO rods cannot be explained by cell stress induced by persistent signaling, since it is not prevented by the removal of transducin, the visual G-protein, nor can it be explained by downregulation of protein phosphatase 2A, the putative rhodopsin phosphatase. We further show that cone arrestin (ARR4), which binds light-activated, phosphorylated rhodopsin poorly, had little effect in enhancing rhodopsin dephosphorylation, whereas mice expressing binding-competent mutant ARR1-3A showed a similar time course of rhodopsin dephosphorylation as WT. Together, these results reveal a novel role of ARR1 in facilitating rhodopsin dephosphorylation in vivoSIGNIFICANCE STATEMENT G-protein-coupled receptors (GPCRs) are transmembrane proteins used by cells to receive and respond to a broad range of extracellular signals that include neurotransmitters, hormones, odorants, and light (photons). GPCR signaling is terminated by two sequential steps: phosphorylation and arrestin binding. Both steps must be reversed when GPCRs are recycled and reused. Dephosphorylation, which is required for recycling, is an understudied process. Using rhodopsin as a prototypical GPCR, we discovered that arrestin facilitated rhodopsin dephosphorylation in living mice.

Understanding the Effects of Anesthesia on Cortical Electrophysiological Recordings: A Scoping Review

General anesthesia in animal experiments is an ethical must and is required for all the procedures that are likely to cause more than slight or momentary pain. As anesthetics are known to deeply affect experimental findings, including electrophysiological recordings of brain activity, understanding their mechanism of action is of paramount importance. It is widely recognized that the depth and type of anesthesia introduce significant bias in electrophysiological measurements by affecting the shape of both spontaneous and evoked signals, e.g., modifying their latency and relative amplitude. Therefore, for a given experimental protocol, it is relevant to identify the appropriate anesthetic, to minimize the impact on neuronal circuits and related signals under investigation. This review focuses on the effect of different anesthetics on cortical electrical recordings, examining their molecular mechanisms of action, their influence on neuronal microcircuits and, consequently, their impact on cortical measurements.

Severe Neuroexcitatory Reaction: A Rare and Underrecognized Life-Threatening Complication of Propofol-Induced Anesthesia

We describe a case of severe neuroexcitatory reaction with hyperthermia after administration of propofol in a 43-year-old patient suspected of a relapse of sarcoidosis who underwent bronchoscopy. This resulted in a lengthy stay in intensive care and long-term neuropsychological impairment. A review of the literature shows that severe neuroexcitatory symptoms (seizure-like phenomena, abnormal hypertonic, and/or jerky movements) occur rarely after propofol administration and may be life-threatening. Due to the paucity of data, the treatment is mostly empirical. The diagnosis can also be delayed owing to underrecognition. We conclude that health practitioners who frequently use propofol should be aware of this specific manifestation of drug toxicity, which albeit rare can be devastating for the patient.

Propofol reduces microglia activation and neurotoxicity through inhibition of extracellular vesicle release

Propofol is an established anesthetic widely used for induction and maintenance of anesthesia. We investigated propofol for its anti-inflammatory effects on microglia and found that propofol treatment is associated with substantial lower levels of extracellular vesicles (EVs) in immune activated microglia. Importantly, EVs collected from immune activated microglia reversed propofol-mediated anti-inflammatory and neuroprotective effects, suggesting that propofol reduces proinflammatory microglia activation and microglia-mediated neurotoxicity through inhibition of EV release. These data shed new insight into a novel molecular mechanism of propofol-mediated neuroprotective and immunomodulatory effects through inhibition of EV release.

Effects of propofol on conditioned place preference in male rats: Involvement of nitrergic system

BACKGROUND

Drug-induced conditioned place preference (CPP) is linked to the addictive properties of the drug used. The number of studies that have investigated the effects of propofol on CPP is limited. Research findings suggest that nitric oxide (NO) might play an important role in substance use disorders.

OBJECTIVES

The present study sought to investigate the role of the nitrergic system on the rewarding effects of propofol by using the CPP protocol in rats.

METHODS

The experiment followed habituation, pre-conditioning, conditioning, and post conditioning sessions. Male Wistar albino rats weighing 240-290 g were divided into eight groups: control (saline), propofol (10, 20, and 40 mg/kg), the NO synthase (NOS) inhibitor N^G-nitro-L-arginine methyl ester (L-NAME) alone (30 and 60 mg/kg), and in combination with propofol (30 and 60 mg/kg L-NAME plus 40 mg/kg propofol) (n = 8 for each group). The CPP effects of propofol, L-NAME, saline, and their combinations were evaluated. All the drug and saline administrations were performed by intraperitoneal (ip) injections.

RESULTS

Propofol (10-40 mg/kg) produced CPP that was statistically significant relative to saline. Propofol-induced CPP was significantly reversed by pretreatment with L-NAME. When administered alone, L-NAME did not produce CPP and also did not produce any significant change on locomotor activity of naïve rats.

CONCLUSION

Our results suggest that propofol produces CPP effects in rats and that NO-related mechanisms may be responsible for propofol-induced CPP. Thus, propofol might have the potential to be addictive, and this possibility should be considered during clinical applications of this drug.

Assessment of different anesthesia depth under total intravenous anesthesia on postoperative cognitive function in laparoscopic patients

Background:

This study aimed to compare the effects of different depths of sedation during total intravenous anesthesia (TIVA) with remifentanil and propofol given by target-controlled infusion (TCI) on postoperative cognitive function in young and middle-aged patients undergoing gynecological laparoscopic surgery.

Materials and Methods:

A total of 150 American Society of Anesthesiologists physical Status I/II patients scheduled for gynecological laparoscopic operation were randomly divided into three groups. Anesthesia was maintained with intravenous infusion of TCI propofol and remifentanil, intermittent injected intravenously with rocuronium. The infusion concentration of propofol and remifentanil was adjusted to maintain bispectral index (BIS) at 30 < BIS ≤ 40 in the first group, 40 < BIS ≤ 50 in the second group, and 50 < BIS ≤ 60 in the third group. Mini–mental state examination (MMSE) and trail-making test (TMT) were used to assess the cognitive function one day preoperatively and one day postoperatively.

Results:

MMSE scores were > 24 sores on the day before anesthesia and the day after surgery in all three groups. However, the first group had the significantly higher MMSE scores than the other two groups after surgery (P < 0.05). Compared with that before anesthesia, TMT completion time was shorter on the day after surgery in the first group, while prolonged in the third group (P < 0.05). The first group had the significantly lower TMT completion time than the other two groups (P < 0.05).

Conclusion:

The depth of sedation, 30 < BIS value ≤ 40, under TIVA with remifentanil and propofol given by TCI had the minimal influence on postoperative cognitive function.

Endocannabinoids as Guardians of Metastasis

Endocannabinoids including anandamide and 2-arachidonoylglycerol are involved in cancer pathophysiology in several ways, including tumor growth and progression, peritumoral inflammation, nausea and cancer pain. Recently we showed that the endocannabinoid profiles are deranged during cancer to an extent that this manifests in alterations of plasma endocannabinoids in cancer patients, which was mimicked by similar changes in rodent models of local and metastatic cancer. The present topical review summarizes the complexity of endocannabinoid signaling in the context of tumor growth and metastasis.

Impact of malnutrition on propofol consumption and recovery time among patients undergoing laparoscopic gastrointestinal surgery

BACKGROUND

Malnutrition is a major health problem, especially in hospitalized patients as it can be closely related to many post-operative complications. However, research on malnutrition and its effect on the outcome of general anesthesia have been largely neglected. Here we investigated malnutrition status on propofol consumption and recovery time among patients undergoing laparoscopic gastrointestinal surgery under general anesthesia.

METHODS

One hundred and one patients were recruited between January and June 2012 at Tongji Hospital and assigned into three groups according to Nutritional Risk Screening Tool 2002 score. A standard combined general anesthesia procedure was performed under regular monitoring. The dosage of propofol needed for induction, consumption during maintenance and recovery time were recorded.

RESULTS

When compared with normal nutritional status individuals, the propofol dosage at induction was significantly decreased about 4.3% in moderate malnutritional status patients (P < 0.01) and about 16.8% in severely malnutritional status patients (P < 0.01). The average consumption of propofol was also significantly lower in malnourished individuals; for moderate malnutritional, the decrease was about 20% (P < 0.01) while for the severely malnutritional, it was 30% (P < 0.01) when compared with normal nutritional status individuals. For the recovery time of propofol anesthesia, the patients with severe malnutritional status awoke average 6.8 min later than those normally nourished (P < 0.01), but those patients with moderate malnutrition status did not (P = 0.885).

CONCLUSION

The present results indicate that the dosage and recovery time of propofol does change in malnourished individuals. Therefore, malnutrition may somehow affect the outcome of general anesthesia.

GABA(A) receptor pi (GABRP) stimulates basal-like breast cancer cell migration through activation of extracellular-regulated kinase 1/2 (ERK1/2)

Breast cancer is a heterogeneous disease comprised of distinct subtypes predictive of patient outcome. Tumors of the basal-like subtype have a poor prognosis due to inherent aggressiveness and the lack of targeted therapeutics. Basal-like tumors typically lack estrogen receptor-α, progesterone receptor and HER2/ERBB2, or in other words they are triple negative (TN). Continued evaluation of basal-like breast cancer (BLBC) biology is essential to identify novel therapeutic targets. Expression of the pi subunit of the GABA(A) receptor (GABRP) is associated with the BLBC/TN subtype, and herein, we reveal its expression also correlates with metastases to the brain and poorer patient outcome. GABRP expression in breast cancer cell lines also demonstrates a significant correlation with the basal-like subtype suggesting that GABRP functions in the initiation and/or progression of basal-like tumors. To address this postulate, we stably silenced GABRP in two BLBC cell lines, HCC1187 and HCC70 cells. Decreased GABRP reduces in vitro tumorigenic potential and migration concurrent with alterations in the cytoskeleton, specifically diminished cellular protrusions and expression of the BLBC-associated cytokeratins, KRT5, KRT6B, KRT14, and KRT17. Silencing GABRP also decreases phosphorylation of extracellular regulated kinase 1/2 (ERK1/2) in both cell lines and selective inhibition of ERK1/2 similarly decreases the basal-like cytokeratins as well as migration. Combined, these data reveal a GABRP-ERK1/2-cytokeratin axis that maintains the migratory phenotype of basal-like breast cancer. GABRP is a component of a cell surface receptor, thus, these findings suggest that targeting this new signaling axis may have therapeutic potential in BLBC.

Total intravenous anaesthesia with high-dose remifentanil does not aggravate postoperative nausea and vomiting and pain, compared with low-dose remifentanil: a double-blind and randomized trial

The study was designed to investigate postoperative nausea and vomiting (PONV) in low- and high-dose remifentanil regimens for total intravenous anaesthesia (TIVA) in adult female patients with American Society of Anaesthesiologists physical status classification I undergoing local breast excision. Propofol and remifentanil 5 ng · mL(-1) (L group) or 10 ng · mL(-1) (H group) were administered for anaesthesia induction and maintenance. Propofol was titrated within range of 0.1 μg · mL(-1) to maintain bispectral index (BIS) values between 40 and 60. Haemodynamic parameters during the intra- and postoperative periods and 24 h postoperative visual analogue scale (VAS) and PONV were evaluated. Each group with 63 patients was analyzed. The H group showed higher use of remifentanil and lower use of propofol, with similar recovery time. Mean systemic arterial blood pressure (MBP), heart rate, and BIS did not differ significantly before and after endotracheal intubation in the H group. However, significant increases in MBP and BIS were apparent in the L group. Postoperative VAS, PONV incidence and scale, and Rhodes index did not differ significantly between the two groups. In conclusion, TIVA with high-dose remifentanil did not aggravate PONV with similar postoperative pain, compared with low-dose remifentanil. Furthermore, high-dose remifentanil showed more haemodynamic stability after endotracheal intubation. This trial is registered with KCT0000185.

Therapeutic potential of small molecules and engineered proteins

Virtually all currently used therapeutic agents are small molecules, largely because the development and delivery of small molecule drugs is relatively straightforward. Small molecules have serious limitations: drugs of this type can be fairly good enzyme inhibitors, receptor ligands, or allosteric modulators. However, most cellular functions are mediated by protein interactions with other proteins, and targeting protein-protein interactions by small molecules presents challenges that are unlikely to be overcome with these compounds as the only tools. Recent advances in gene delivery techniques and characterization of cell type-specific promoters open the prospect of using reengineered signaling-biased proteins as next-generation therapeutics. The first steps in targeted engineering of proteins with desired functional characteristics look very promising. As quintessential scaffolds that act strictly via interactions with other proteins in the cell, arrestins represent a perfect model for the development of these novel therapeutic agents with enormous potential: custom-designed signaling proteins will allow us to tell the cell what to do and when to do it in a way it cannot disobey.

Arrestin-dependent activation of JNK family kinases

The activity of all mitogen-activated protein kinases (MAPKs) is stimulated via phosphorylation by upstream MAPK kinases (MAPKK), which are in their turn activated via phosphorylation by MAPKK kinases (MAPKKKs). The cells ensure the specificity of signaling in these cascades by employing a variety of scaffolding proteins that bind matching MAPKKKs, MAPKKs, and MAPKs. All four vertebrate arrestin subtypes bind JNK3, but only arrestin-3 serves as a scaffold, promoting JNK3 activation in intact cells. Arrestin-3-mediated JNK3 activation does not depend on arrestin-3 interaction with G protein-coupled receptors (GPCRs), as demonstrated by the ability of some arrestin mutants that cannot bind receptors to activate JNK3, whereas certain mutants with enhanced GPCR binding fail to promote JNK3 activation. Recent findings suggest that arrestin-3 directly binds both MAPKKs necessary for JNK activation and facilitates JNK3 phosphorylation at both Thr (by MKK4) and Tyr (by MKK7). JNK3 is expressed in a limited set of cell types, whereas JNK1 and JNK2 isoforms are as ubiquitous as arrestin-3. Recent study showed that arrestin-3 facilitates the activation of JNK1 and JNK2, scaffolding MKK4/7-JNK1/2/3 signaling complexes. In all cases, arrestin-3 acts by bringing the kinases together: JNK phosphorylation shows biphasic dependence on arrestin-3, being enhanced at lower and suppressed at supraoptimal concentrations. Thus, arrestin-3 regulates the activity of multiple JNK isoforms, suggesting that it might play a role in survival and apoptosis of all cell types.

Synergistic activation of lipopolysaccharide-stimulated glial cells by propofol

Despite the extensive use of propofol in general anesthetic procedures, the effects of propofol on glial cell were not completely understood. In lipopolysaccharide (LPS)-stimulated rat primary astrocytes and BV2 microglial cell lines, co-treatment of propofol synergistically induced inflammatory activation as evidenced by the increased production of NO, ROS and expression of iNOS, MMP-9 and several cytokines. Propofol augmented the activation of JNK and p38 MAPKs induced by LPS and the synergistic activation of glial cells by propofol was prevented by pretreatment of JNK and p38 inhibitors. When we treated BV2 cell culture supernatants treated with LPS plus propofol on cultured rat primary neuron, it induced a significant neuronal cell death. The results suggest that the repeated use of propofol in immunologically challenged situation may induce glial activation in brain.

The modern pharmacology of paracetamol: therapeutic actions, mechanism of action, metabolism, toxicity and recent pharmacological findings

Paracetamol is used worldwide for its analgesic and antipyretic actions. It has a spectrum of action similar to that of NSAIDs and resembles particularly the COX-2 selective inhibitors. Paracetamol is, on average, a weaker analgesic than NSAIDs or COX-2 selective inhibitors but is often preferred because of its better tolerance. Despite the similarities to NSAIDs, the mode of action of paracetamol has been uncertain, but it is now generally accepted that it inhibits COX-1 and COX-2 through metabolism by the peroxidase function of these isoenzymes. This results in inhibition of phenoxyl radical formation from a critical tyrosine residue essential for the cyclooxygenase activity of COX-1 and COX-2 and prostaglandin (PG) synthesis. Paracetamol shows selectivity for inhibition of the synthesis of PGs and related factors when low levels of arachidonic acid and peroxides are available but conversely, it has little activity at substantial levels of arachidonic acid and peroxides. The result is that paracetamol does not suppress the severe inflammation of rheumatoid arthritis and acute gout but does inhibit the lesser inflammation resulting from extraction of teeth and is also active in a variety of inflammatory tests in experimental animals. Paracetamol often appears to have COX-2 selectivity. The apparent COX-2 selectivity of action of paracetamol is shown by its poor anti-platelet activity and good gastrointestinal tolerance. Unlike both non-selective NSAIDs and selective COX-2 inhibitors, paracetamol inhibits other peroxidase enzymes including myeloperoxidase. Inhibition of myeloperoxidase involves paracetamol oxidation and concomitant decreased formation of halogenating oxidants (e.g. hypochlorous acid, hypobromous acid) that may be associated with multiple inflammatory pathologies including atherosclerosis and rheumatic diseases. Paracetamol may, therefore, slow the development of these diseases. Paracetamol, NSAIDs and selective COX-2 inhibitors all have central and peripheral effects. As is the case with the NSAIDs, including the selective COX-2 inhibitors, the analgesic effects of paracetamol are reduced by inhibitors of many endogenous neurotransmitter systems including serotonergic, opioid and cannabinoid systems. There is considerable debate about the hepatotoxicity of therapeutic doses of paracetamol. Much of the toxicity may result from overuse of combinations of paracetamol with opioids which are widely used, particularly in USA.

Eicosanoid regulation of hematopoiesis and hematopoietic stem and progenitor trafficking

Hematopoietic stem cell (HSC) transplantation is a potentially curative treatment for numerous hematological malignancies. The transplant procedure as performed today takes advantage of HSC trafficking; either egress of HSC from the bone marrow to the peripheral blood, that is, mobilization, for acquisition of the hematopoietic graft, and/or trafficking of HSC from the peripheral blood to bone marrow niches in the recipient patient, that is HSC homing. Numerous studies, many of which are reviewed herein, have defined hematopoietic regulatory mechanisms mediated by the 20-carbon lipid family of eicosanoids, and recent evidence strongly supports a role for eicosanoids in regulation of hematopoietic trafficking, adding a new role whereby eicosanoids regulate hematopoiesis. Short-term exposure of HSC to the eicosanoid prostaglandin E(2) increases CXCR4 receptor expression, migration and in vivo homing of HSC. In contrast, cannabinoids reduce hematopoietic progenitor cell (HPC) CXCR4 expression and induce HPC mobilization when administered in vivo. Leukotrienes have been shown to alter CD34(+) cell adhesion, migration and regulate HSC proliferation, suggesting that eicosanoids have both opposing and complimentary roles in the regulation of hematopoiesis. As numerous FDA approved compounds regulate eicosanoid signaling or biosynthesis, the utility of eicosanoid-based therapeutic strategies to improve hematopoietic transplantation can be rapidly evaluated.

Role of the cannabinoid system in pain control and therapeutic implications for the management of acute and chronic pain episodes

Cannabis extracts and synthetic cannabinoids are still widely considered illegal substances. Preclinical and clinical studies have suggested that they may result useful to treat diverse diseases, including those related with acute or chronic pain. The discovery of cannabinoid receptors, their endogenous ligands, and the machinery for the synthesis, transport, and degradation of these retrograde messengers, has equipped us with neurochemical tools for novel drug design. Agonist-activated cannabinoid receptors, modulate nociceptive thresholds, inhibit release of pro-inflammatory molecules, and display synergistic effects with other systems that influence analgesia, especially the endogenous opioid system. Cannabinoid receptor agonists have shown therapeutic value against inflammatory and neuropathic pains, conditions that are often refractory to therapy. Although the psychoactive effects of these substances have limited clinical progress to study cannabinoid actions in pain mechanisms, preclinical research is progressing rapidly. For example, CB(1)mediated suppression of mast cell activation responses, CB(2)-mediated indirect stimulation of opioid receptors located in primary afferent pathways, and the discovery of inhibitors for either the transporters or the enzymes degrading endocannabinoids, are recent findings that suggest new therapeutic approaches to avoid central nervous system side effects. In this review, we will examine promising indications of cannabinoid receptor agonists to alleviate acute and chronic pain episodes. Recently, Cannabis sativa extracts, containing known doses of tetrahydrocannabinol and cannabidiol, have granted approval in Canada for the relief of neuropathic pain in multiple sclerosis. Further double-blind placebo-controlled clinical trials are needed to evaluate the potential therapeutic effectiveness of various cannabinoid agonists-based medications for controlling different types of pain.

Pitfalls and solutions in assaying anandamide transport in cells

Nonspecific binding of anandamide to plastic exhibits many features that could be mistaken as biological processes, thereby representing an important source of conflicting data on the uptake and release of this lipophilic substance. Herein, we propose an improved method to assay anandamide transport, by using glass slides (i.e., coverslips) as physical support to grow cells. Although the results obtained using plastic do not differ significantly from those obtained using glass, the new procedure has the advantage of being faster, simpler, and more accurate. In fact, the lack of aspecific adsorption of anandamide to the glass surface yields a lower background and a higher precision and accuracy in determining transport kinetics, especially for the export process. Remarkably, the kinetic parameters of anandamide uptake obtained with the old and the new procedures may be similar or different depending on the cell type, thus demonstrating the complexity of the interference of plastic on the transport process. In addition, the novel procedure is particularly suitable for visualization and measurement of anandamide transport in intact cells by using a biotinylated derivative in confocal fluorescence microscopy.

Sleep in the ICU: potential mechanisms and clinical implications

Patients in the ICU are known to have severely disrupted sleep with disturbed circadian pattern, decreased nocturnal sleep time, abnormally increased stages 1 and 2 sleep, and reduced or absent deep sleep. Recent data reveal that a subpopulation of critically ill patients manifests unique EEG sleep patterns. The etiology of sleep disruption in the ICU includes the inherent nature of the environment, medications, ventilator-patient interaction, and the effect of acute illness. How sleep disruption contributes to outcomes in critically ill patients, such as recovery time and weaning from mechanical ventilation, is unknown. This article reviews the literature describing sleep in ICU patients, including recent investigations in patients who require mechanical ventilation, factors that affect sleep in critically ill patients, and the potential mechanisms and clinical implications of disturbed sleep in the ICU setting with directions to consider for future investigations.

Propofol: neuroprotection in an in vitro model of traumatic brain injury

Introduction

The anaesthetic agent propofol (2,6-diisopropylphenol) has been shown to be an effective neuroprotective agent in different in vitro models of brain injury induced by oxygen and glucose deprivation. We examined its neuroprotective properties in an in vitro model of traumatic brain injury.

Methods

In this controlled laboratory study organotypic hippocampal brain-slice cultures were gained from six- to eight-day-old mice pups. After 14 days in culture, hippocampal brain slices were subjected to a focal mechanical trauma and subsequently treated with different molar concentrations of propofol under both normo- and hypothermic conditions. After 72 hours of incubation, tissue injury assessment was performed using propidium iodide (PI), a staining agent that becomes fluorescent only when it enters damaged cells via perforated cell membranes. Inside the cell, PI forms a fluorescent complex with nuclear DNA.

Results

A dose-dependent reduction of both total and secondary tissue injury could be observed in the presence of propofol under both normo- and hypothermic conditions. This effect was further amplified when the slices were incubated at 32°C after trauma.

Conclusions

When used in combination, the dose-dependent neuroprotective effect of propofol is additive to the neuroprotective effect of hypothermia in an in vitro model of traumatic brain injury.

Endocannabinoid-mediated control of synaptic transmission

The discovery of cannabinoid receptors and subsequent identification of their endogenous ligands (endocannabinoids) in early 1990s have greatly accelerated research on cannabinoid actions in the brain. Then, the discovery in 2001 that endocannabinoids mediate retrograde synaptic signaling has opened up a new era for cannabinoid research and also established a new concept how diffusible messengers modulate synaptic efficacy and neural activity. The last 7 years have witnessed remarkable advances in our understanding of the endocannabinoid system. It is now well accepted that endocannabinoids are released from postsynaptic neurons, activate presynaptic cannabinoid CB(1) receptors, and cause transient and long-lasting reduction of neurotransmitter release. In this review, we aim to integrate our current understanding of functions of the endocannabinoid system, especially focusing on the control of synaptic transmission in the brain. We summarize recent electrophysiological studies carried out on synapses of various brain regions and discuss how synaptic transmission is regulated by endocannabinoid signaling. Then we refer to recent anatomical studies on subcellular distribution of the molecules involved in endocannabinoid signaling and discuss how these signaling molecules are arranged around synapses. In addition, we make a brief overview of studies on cannabinoid receptors and their intracellular signaling, biochemical studies on endocannabinoid metabolism, and behavioral studies on the roles of the endocannabinoid system in various aspects of neural functions.

Expression of the endocannabinoid system in fibroblasts and myofascial tissues

The endocannabinoid (eCB) system, like the better-known endorphin system, consists of cell membrane receptors, endogenous ligands and ligand-metabolizing enzymes. Two cannabinoid receptors are known: CB(1) is principally located in the nervous system, whereas CB(2) is primarily associated with the immune system. Two eCB ligands, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are mimicked by cannabis plant compounds. The first purpose of this paper was to review the eCB system in detail, highlighting aspects of interest to bodyworkers, especially eCB modulation of pain and inflammation. Evidence suggests the eCB system may help resolve myofascial trigger points and relieve symptoms of fibromyalgia. However, expression of the eCB system in myofascial tissues has not been established. The second purpose of this paper was to investigate the eCB system in fibroblasts and other fascia-related cells. The investigation used a bioinformatics approach, obtaining microarray data via the GEO database (www.ncbi.nlm.nih.gov/geo/). GEO data mining revealed that fibroblasts, myofibroblasts, chondrocytes and synoviocytes expressed CB(1), CB(2) and eCB ligand-metabolizing enzymes. Fibroblast CB(1) levels nearly equalled levels expressed by adipocytes. CB(1) levels upregulated after exposure to inflammatory cytokines and equiaxial stretching of fibroblasts. The eCB system affects fibroblast remodeling through lipid rafts associated with focal adhesions and dampens cartilage destruction by decreasing fibroblast-secreted metalloproteinase enzymes. In conclusion, the eCB system helps shape biodynamic embryological development, diminishes nociception and pain, reduces inflammation in myofascial tissues and plays a role in fascial reorganization. Practitioners wield several tools that upregulate eCB activity, including myofascial manipulation, diet and lifestyle modifications, and pharmaceutical approaches.

Modulation of Remifentanil-Induced Postinfusion Hyperalgesia by Propofol

BACKGROUND

Experimental and clinical studies suggest that brief opioid exposure can enhance pain sensitivity. During anesthesia, however, opioids are commonly administered in combination with either IV or inhaled hypnotic drugs. In this investigation we sought to determine the analgesic and antihyperalgesic properties of propofol in subhypnotic concentrations on remifentanil-induced postinfusion hypersensitivity in an experimental human pain model.

METHODS

Fifteen healthy volunteers were included in this randomized, double-blind, and placebo-controlled study in a cross-over design. Transcutaneous electrical stimulation at high current densities (41.7 +/- 14.3 mA) induced spontaneous acute pain (numerical rating scale = 6 of 10) and stable areas of hyperalgesia. Pain intensities and areas of hyperalgesia were assessed before, during and after a 30 min target-controlled infusion of propofol (1.5 microg/mL) and remifentanil (0.05 microg x kg(-1) x min(-1)), either alone or in combination (propofol 1.5 microg/mL with remifentanil 0.025 or 0.05 microg x kg(-1) x min(-1)).

RESULTS

During infusion, propofol significantly reduced the electrically evoked pain to 72% +/- 21% of control. Subhypnotic concentrations of propofol did not lead to any hyperalgesic effects. Coadministration of remifentanil led to synergistic analgesic effects (to 62% +/- 26% and 58% +/- 25% of control, for 0.025 or 0.05 microg x kg(-1) x min(-1), respectively), but upon withdrawal, pain and hyperalgesia increased above control level.

CONCLUSIONS

The results suggest clinically relevant interactions of propofol and remifentanil in humans, since propofol led to a delay and a weakening of remifentanil-induced postinfusion anti-analgesia in humans. Nevertheless, pronociceptive effects were not completely antagonized by propofol, which may account for the increased demand for analgesics after remifentanil-based anesthesia in clinical practice.

The Antinociceptive Effects of Local Injections of Propofol in Rats Are Mediated in Part by Cannabinoid CB1 and CB2 Receptors

BACKGROUND

Propofol can inhibit fatty acid amidohydrolase, the enzyme responsible for the metabolism of anandamide (an endocannabinoid). To study the potential antinociceptive effect of propofol, we administered different doses (0.005, 0.05, 0.5, 5, and 500 microg) of the anesthetic in the hind paw of animals to determine an ED50. To further investigate the mechanisms by which propofol produced its antinociceptive effect, we used specific antagonists for the cannabinoid CB1 (AM251) and CB2 (AM630) receptors and measured fatty-acid amide/endocannabinoid (anandamide, 2-arachidonylglycerol, and palmitoylethanolamide) concentrations in skin paw tissues.

METHODS

Formalin tests were performed on 65 Wistar rats allocated to six different groups: 1) control (Intralipidtrade mark 10%); 2) propofol (ED50 dose); 3) AM251; 4) AM251 + propofol; 5) AM630; 6) AM630 + propofol. Drugs were injected subcutaneously in the dorsal surface of the hind paw (50 microL) 15 min before 2.5% formalin injection into the same paw. Fatty-acid amide/endocannabinoid levels were measured by high performance liquid chromatography/mass spectrometry analysis.

RESULTS

Propofol produced a dose-dependent antinociceptive effect for the early and late phases of the formalin test with an ED50 of 0.08 +/- 0.061 microg for the latter phase. This effect was antagonized by AM251 and AM630. It was locally mediated, since a higher dose of propofol given in the contralateral paw was not antinociceptive. Finally, only paw concentrations of palmitoylethanolamide were significantly increased.

CONCLUSION

In a test of inflammatory pain, locally injected propofol decreased pain behavior in a dose-dependent manner. This antinociceptive effect was mediated, in part, by CB1 and CB2 receptors.

Jekyll and hyde: two faces of cannabinoid signaling in male and female fertility

Mammalian reproduction is a complicated process designed to diversify and strengthen the genetic complement of the offspring and to safeguard regulatory systems at various steps for propagating procreation. An emerging concept in mammalian reproduction is the role of endocannabinoids, a group of endogenously produced lipid mediators, that bind to and activate cannabinoid receptors. Although adverse effects of cannabinoids on fertility have been implicated for years, the mechanisms by which they exert these effects were not clearly understood. With the identification of cannabinoid receptors, endocannabinoid ligands, their key synthetic and hydrolytic pathways, and the generation of mouse models missing cannabinoid receptors, a wealth of information on the significance of cannabinoid/endocannabinoid signaling in spermatogenesis, fertilization, preimplantation embryo development, implantation, and postimplantation embryonic growth has been generated. This review focuses on various aspects of the endocannabinoid system in male and female fertility. It is hoped that a deeper insight would lead to potential clinical applications of the endocannabinoid signaling as a target for correcting infertility and improving reproductive health in humans.

Soluble mimics of the cytoplasmic face of the human V1-vascular vasopressin receptor bind arrestin2 and calmodulin

Signal transduction by G protein-coupled receptors (GPCRs) is mediated by interactions between intracellular proteins and exposed motifs on the cytoplasmic face of these receptors. Arrestins bind to GPCRs and modulate receptor function either by interfering with heterotrimeric G protein signaling or by serving as signaling adaptors themselves. Calmodulin interacts with GPCRs triggering a calcium response. We have studied the interaction of arrestin2 and calmodulin with intracellular elements of the human V1-vascular vasopressin receptor (hV1R). For this purpose, we designed, expressed, and purified soluble fusion proteins with the maltose-binding protein (MBP) from Escherichia coli that mimic the intracellular surface of the hV1R. These MBP fusion proteins bind arrestin2 and calmodulin with affinities in the micromolar range. A different series of soluble receptor analogs, named vasopressin receptor 1 elements on a soluble scaffold (V1ROSS) proteins, consist of the third intracellular loop and/or the C-terminal segment of the hV1R receptor juxtaposed on the surface of the MBP. V1ROSS proteins bind calmodulin and a truncated, phosphorylation-independent form of arrestin2 more tightly than the corresponding linear fusion proteins. Thus, embedding receptor loops within the three-dimensional structure of the MBP yields a better representation of the active conformation of these receptor loops than linear receptor peptides fused onto the C terminus of the MBP. V1ROSS proteins provide a valuable tool to study receptor interactions because they are more amenable to structural analysis than the native membrane receptor. These findings set the stage for the detailed structural analysis of these protein-protein interactions that are important for understanding the mechanism of signaling.

Oral treatment options for degenerative joint disease--presence and future

Alleviation of pain and inhibition of inflammation are the primary goals of pharmacotherapy of osteoarthritis (OA). These therapeutic goals can almost always be accomplished by the use of analgesics and nonsteroidal anti-inflammatory drugs (NSAID). One of the main problems of NSAIDs is their gastrointestinal toxicity, for which a prophylactic medication should be considered particularly amongst risk groups. Recent studies have shown that COX-2-selective and maybe also non-selective NSAIDs increase the cardiovascular risk so that their application is getting now drastically restricted. Pharmacological results published until now suggest that a clinically relevant minor analgesic and/or anti-inflammatory effect can be attained with the use of some of the SYmptomatic Slow Acting Drugs in OA (SYSADOAs). However, no clinical studies exist, which can positively confirm prevention, slowing down or reversal of any advanced joint cartilage destruction by any individual medication. Disease modifying therapy is still in its infancy; discovery and development of novel therapeutic targets and agents are an extremely difficult task, currently challenging many pharmaceutical companies and academic institutions.

First “hybrid” ligands of vanilloid TRPV1 and cannabinoid CB2receptors and non-polyunsaturated fatty acid-derived CB2-selective ligands

12-Phenylacetyl-ricinoleoyl-vanillamide (phenylacetylrinvanil, PhAR, IDN5890), is an ultra-potent agonist of human vanilloid TRPV1 receptors also endowed with moderate affinity for human cannabinoid CB(2) receptors. To improve its CB(2) affinity and temper its potency at TRPV1, the modification of the polar headgroup and the lipophilic 12-acylgroup of PhAR was pursued. Replacement of the vanillyl headgroup of PhAR with various aromatic or alkyl amino groups decreased activity at TRPV1 receptors, although the dopamine, cyclopropylamine, 1'-(R)- and 1'-(S)-methyl-ethanolamine, and ethanolamine derivatives retained significant potency (EC(50) 31-126 nM). Within these compounds, the 12-phenylacetylricinoleyl cyclopropylamide and ethanolamide were the strongest ligands at CB(2) receptors, with K(i) of 22 and 44 nM, and 14- and >20-fold selectivity over cannabinoid CB(1) receptors, respectively. The propyl- and allyl-derivatives also exhibited high affinity at CB(2) receptors (K(i)=40 and 22 nM, with 40 and >80-fold selectivity over CB(1) receptors, respectively), but no activity at TRPV1 receptors. The cyclopropyl- and allyl-derivatives behaved as CB(2) inverse agonists in the GTP-gamma-S binding assay. Addition of para-methoxy, -tert-butyl or -chlorine groups to the 12-phenylacetyl moiety of PhAR produced compounds that retained full potency at TRPV1 receptors, but with improved selectivity over CB(2) or CB(1) receptors. Thus, the manipulation of PhAR led to the development of the first CB(2)/TRPV1 dual ligands and of an entirely new class of inverse agonists at CB(2) receptors. Both types of compounds might find application in the treatment of inflammation, and represent new molecular probes to investigate the endocannabinoid-endovanilloid signalling system.

Keynote review: Medicinal chemistry strategies to CB1 cannabinoid receptor antagonists

The proven clinical efficacy of the CB(1) cannabinoid receptor antagonist rimonabant in both obesity and smoking cessation and its therapeutic potential in other disorders has given a tremendous impetus to the discovery of novel CB(1) antagonists. The number of disclosed patents wherein novel chemical entities having CB(1) antagonistic or inverse agonistic properties have been claimed has exploded. Besides novel compound classes that were identified in screening, rational medicinal chemistry approaches such as conformational constraint and scaffold hopping have been successfully applied. CB(1) receptor modelling has provided insight into crucial receptor-ligand interaction points thereby leading to a general CB(1) inverse agonist pharmacophore model.