Tissue Engineering of Cartilage; Can Cannabinoids Help?

This review discusses the role of the cannabinoid system in cartilage tissue and endeavors to establish if targeting the cannabinoid system has potential in mesenchymal stem cell based tissue-engineered cartilage repair strategies. The review discusses the potential of cannabinoids to protect against the degradation of cartilage in inflamed arthritic joints and the influence of cannabinoids on the chondrocyte precursors, mesenchymal stem cells (MSCs). We provide experimental evidence to show that activation of the cannabinoid system enhances the survival, migration and chondrogenic differentiation of MSCs, which are three major tenets behind the success of a cell-based tissue-engineered cartilage repair strategy. These findings highlight the potential for cannabinoids to provide a dual function by acting as anti-inflammatory agents as well as regulators of MSC biology in order to enhance tissue engineering strategies aimed at cartilage repair.

12-Lipoxygenase is a potential therapeutic target in non-small cell lung cancer

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Background: Platelet-type 12-LOX is an arachidonic acid metabolising enzyme resulting in the formation of 12(S)-HETE, which stimulates tumour cell adhesion, invasion and metastasis. We examined the expression of 12-LOX in NSCLC and its role in cell survival. Methods: A549 (adenocarcinoma), SK-MES1 (squamous cell lung carcinoma), H460 and H647 (large cell lung carcinoma) were grown in serum depleted media (0.5%) and screened for 12-LOX expression by RT-PCR and western blot analysis. Cells were treated with baicalein (10uM), a selective inhibitor of 12-LOX, or 12(S)-HETE (100ng/ml) and cell survival / proliferation determined by BrdU assay. Apoptosis was determined using the multi-parameter apoptosis kit and In-cell Analyser, and also by FACS. Gene alterations following 12-LOX inhibition in both A549 and SKMES-1 cells were assessed by quantitative PCR arrays and validated by RT-PCR. A panel of retrospective resected lung tumours were stained for 12-LOX expression by immunhistochemistry. Results: All lung cancer cells lines expressed moderate levels of platelet-type 12-LOX, which was reduced following treatment for 24h with the baicalein. Baicalein decreased lung cancer survival in all cell lines, while 12(S)-HETE increased cellular proliferation. Inhibition of 12-LOX induced apoptosis in a dose dependent manner, with decreased f-actin filaments and loss of mitochondrial mass potential. QPCR array data implicated a number of genes regulating these effects which were validated by RT-PCR, many of which control apoptosis and angiogenesis. The subset of genes downregulated included bcl-2, VEGF, integrin a2 and a4. 12-LOX expression was observed in a variety of human lung cancers with different histological subtypes. Conclusions: 12- LOX is a survival factor in NSCLC. 12-LOX inhibitors decreased NSCLC survival, inducing apoptosis through mechanisms including downregulation of the bcl family of proteins, integrin receptor and angiogenic growth factors. Expression of 12-LOX in fresh resected and retrospective tissue suggests that inhibition of this enzyme is a potential therapeutic strategy in the treatment of NSCLC.

No significant financial relationships to disclose.

Cyclin and cyclin-dependent kinase substrate requirements for preventing rereplication reveal the need for concomitant activation and inhibition

DNA replication initiation in S. cerevisiae is promoted by B-type cyclin-dependent kinase (Cdk) activity. In addition, once-per-cell-cycle replication is enforced by cyclin-Cdk-dependent phosphorylation of the prereplicative complex (pre-RC) components Mcm2-7, Cdc6, and Orc1-6. Several of these controls must be simultaneously blocked by mutation to obtain rereplication. We looked for but did not obtain strong evidence for cyclin specificity in the use of different mechanisms to control rereplication: both the S-phase cyclin Clb5 and the mitotic cyclins Clb1-4 were inferred to be capable of imposing ORC-based and MCM-based controls. We found evidence that the S-phase cyclin Clb6 could promote initiation of replication without blocking reinitiation, and this activity was highly toxic when the ability of other cyclins to block reinitiation was prevented by mutation. The failure of Clb6 to regulate reinitiation was due to rapid Clb6 proteolysis, since this toxic activity of Clb6 was lost when Clb6 was stabilized by mutation. Clb6-dependent toxicity is also relieved when early accumulation of mitotic cyclins is allowed to impose rereplication controls. Cell-cycle timing of rereplication control is crucial: sufficient rereplication block activity must be available as soon as firing begins. DNA rereplication induces DNA damage, and when rereplication controls are compromised, the DNA damage checkpoint factors Mre11 and Rad17 provide additional mechanisms that maintain viability and also prevent further rereplication, and this probably contributes to genome stability.

Influence of strong static magnetic fields on primary cortical neurons

Intense uniform magnetic fields, such as those used in magnetic resonance imaging (MRI), are thought to exert little influence at the cellular level. Here we report modifications of the signaling cascades in rat cortical neurons cultured for 1 h in magnetic fields of up to 5 Tesla. The activation of c-Jun N-terminal kinase (JNK) increases monotonically with field strength, with a maximal activation of approximately 10% at 5 T, whereas the activation of extra cellular-regulated kinase (ERK) shows a maximum at 0.75 T ( approximately 10%). Since ERK is involved in cellular differentiation, these results indicate a magnetic induction of the signaling events associated with differentiation. However, the cells respond to further increases in field strength by evoking a stress response, since JNK is a stress-activated protein kinase. Three possible mechanisms are discussed and of these, the most plausible is magnetic field induced change in the membrane rest potential, a microscale magnetohydrodynamic effect. This mechanism most likely involves the activation of voltage dependent Ca(2+) channel opening; since intracellular Ca(2+) concentration was also found to be modified by the static magnetic field.

Aβ-mediated activation of the apoptotic cascade in cultured cortical neurones: a role for cathepsin-L

Deposition of beta-amyloid protein in the brain is a neuropathological hallmark of Alzheimer's disease. An additional feature of this disease is an upregulation of the lysosomal system, however, the role of lysosomal proteins in the pathogenesis of this neurodegenerative condition is unclear. In this study, we demonstrate that Abeta increases activity of the lysosomal protease, cathepsin-L, and promotes a transient increase in cytosolic expression of cathepsin-L in cultured cortical neurones. The increase in cathepsin-L activity and concentration in the cytosol is evident 6 h following beta-amyloid treatment. The proclivity of beta-amyloid to induce apoptotic changes, such as activation of caspase-3, cleavage of the DNA repair enzyme, poly-ADP ribose polymerase, and DNA fragmentation, were prevented by the selective cathepsin-L inhibitor Z-FF-FMK. In contrast, beta-amyloid had no effect on expression levels or cellular distribution of cathepsin-D and the cathepsin-D inhibitor peptide failed to protect cortical neurones from beta-amyloid-induced apoptosis. Thus, the results from this study demonstrate that beta-amyloid impacts on cathepsin-L as an upstream event in the neurodegenerative process and this result highlights the potential role of lysosomal components in the pathogenesis of Alzheimer's disease.

Acute opioid withdrawal on accidental injection of naltrexone

We report two 16-year-old female intravenous drug users who, after making purchases from street suppliers, both presented with symptoms of acute opioid withdrawal. Urine toxicology revealed naltrexone, a long-acting opioid antagonist used in detoxification and maintenance therapy in opioid dependence. While the safety and efficacy of opiate antagonist treatment is being debated, the present case highlights the vulnerability of this young population. The recent availability of non-prescribed opiate antagonists suggests that both health professionals and young people themselves need to be aware of their effects.

A role for c-Jun N-terminal kinase 1 (JNK1), but not JNK2, in the beta-amyloid-mediated stabilization of protein p53 and induction of the apoptotic cascade in cultured cortical neurons

beta-Amyloid (A beta) peptide has been shown to induce neuronal apoptosis; however, the mechanisms underlying A beta-induced neuronal cell death remain to be fully elucidated. The stress-activated protein kinase, c-Jun N-terminal kinase (JNK), is activated in response to cellular stress and has been identified as a proximal mediator of cell death. In the present study, expression of active JNK was increased in the nucleus and cytoplasm of A beta-treated cells. Evaluation of the nature of the JNK isoforms activated by A beta revealed a transient increase in JNK1 activity that reached its peak at 1 h and a later activation (at 24 h) of JNK2. The tumour suppressor protein, p53, is a substrate for JNK and can serve as a signalling molecule in apoptosis. In cultured cortical neurons, we found that A beta increased p53 protein expression and phosphorylation of p53 at Ser(15). Thus it appears that A beta increases p53 expression via phosphorylation-mediated stabilization of the protein. Given the lack of availability of a JNK inhibitor that can distinguish between JNK1- and JNK2-mediated effects, we employed antisense technology to deplete cells of JNK1 or JNK2 selectively. Using this strategy, the respective roles of JNK1 and JNK2 on the A beta-mediated activation of the apoptotic cascade (i.e. p53 stabilization, caspase 3 activation and DNA fragmentation) were examined. The results obtained demonstrate a role for JNK1 in the A beta-induced stabilization of p53, activation of caspase 3 and DNA fragmentation. In contrast, depletion of JNK2 had no effect on the proclivity of A beta to activate capase 3 or induce DNA fragmentation. These results demonstrate a significant role for JNK1 in A beta-mediated induction of the apoptotic cascade in cultured cortical neurons.

beta-Amyloid (1-40)-induced apoptosis of cultured cortical neurones involves calpain-mediated cleavage of poly-ADP-ribose polymerase

beta-Amyloid((1-40))-induced apoptosis of cultured cortical neurones involves calpain-mediated cleavage of poly-ADP-ribose polymerase. beta-Amyloid protein is thought to contribute to the pathophysiology of Alzheimer's disease by inducing neuronal apoptosis. Our previous work has demonstrated that beta-amyloid activates voltage-dependent Ca(2+) channels in the cortex, resulting in an increase in intracellular Ca(2+) concentration. Calpain is a Ca(2+)-dependent neutral protease which becomes activated following alterations in intracellular Ca(2+) homeostasis. In this study we have demonstrated that beta-amyloid increases calpain activity in cultured cortical neurones in a time-dependent manner. Use of the cell-permeable calpain inhibitor, MDL 28170, has identified cleavage of the DNA-repair enzyme, poly-ADP-ribose polymerase, and DNA fragmentation as downstream consequences of calpain activation. Thus, we propose that the stimulatory effect of beta-amyloid on Ca(2+) influx triggers calpain-mediated DNA fragmentation in cultured cortical neurones.

Delta 9-tetrahydrocannabinol induces the apoptotic pathway in cultured cortical neurones via activation of the CB1 receptor

Delta 9-tetrahydrocannabinol, the principal psychoactive component of marijuana, exerts a variety of effects on the CNS, including impaired cognitive function and neurobehavioural deficits. The mechanisms underlying these neuronal responses to tetrahydrocannabinol are unclear but may involve alterations in neuronal viability. Tetrahydrocannabinol has been shown to influence neuronal survival but the role of the cannabinoid receptors in the regulation of neuronal viability has not been fully clarified. In this study we demonstrate that tetrahydrocannabinol promotes the release of cytochrome c, activates caspase-3, promotes cleavage of the DNA repair enzyme poly-ADP ribose polymerase and induces DNA fragmentation in cultured cortical neurones. These effects of tetrahydrocannabinol were completely abrogated by the CB(1) receptor antagonist AM-251. The findings of this study demonstrate that tetrahydrocannabinol induces apoptosis in cortical neurones in a manner involving the CB1 subtype of cannabinoid receptor.

Lipopolysaccharide inhibits long term potentiation in the rat dentate gyrus by activating caspase-1

Lipopolysaccharide, a component of the cell wall of Gram-negative bacteria, may be responsible for at least some of the pathophysiological sequelae of bacterial infections, probably by inducing an increase in interleukin-1beta (IL-1beta) concentration. We report that intraperitoneal injection of lipopolysaccharide increased hippocampal caspase-1 activity and IL-1beta concentration; these changes were associated with increased activity of the stress-activated kinase c-Jun NH(2)-terminal kinase, decreased glutamate release, and impaired long term potentiation. The degenerative changes in hippocampus and entorhinal cortical neurones were consistent with apoptosis because translocation of cytochrome c and poly(ADP-ribose) polymerase cleavage were increased. Inhibition of caspase-1 blocked these changes, suggesting that IL-1beta mediated the lipopolysaccharide-induced changes.

The role of ceramide in the modulation of intracellular Ca2+ levels by interleukin 1 beta in rat cortical synaptosomes

We recently demonstrated that the pro-inflammatory cytokine, interleukin 1beta (IL-1beta) elevates intracellular free Ca2+ levels ([Ca2+]i) in rat cortical synaptosomes in a manner involving activation of the IL-1 receptor and stimulation of p42 mitogen-activated protein (MAP) kinase. We now report that the effects of IL-1beta on [Ca2+]i are mimicked by the sphingolipid metabolite ceramide. In cortical synaptosomes ceramide elevates [Ca2+]i in a p42 MAP kinase-dependent manner, and we conclude that the effects of IL-1beta on Ca2+ homeostasis involve ceramide as an upstream component of the p42 MAP kinase pathway.

Effect of polyethylene occlusive skin wrapping on heat loss in very low birth weight infants at delivery: a randomized trial

OBJECTIVE

Significant evaporative heat loss in the very low birth weight infant can occur in the delivery room. We investigated the effect of polyethylene wrap applied immediately at birth (without drying) on rectal temperature measured at nursery admission.

STUDY DESIGN

Sixty-two consecutive infants delivered at <32 weeks' gestation were stratified by gestational age and randomly allocated to resuscitation with polyethylene wrap. All infants were resuscitated under radiant warmers. Wraps were removed on nursery admission. Rectal temperature was taken by digital electronic thermometer.

RESULTS

Fifty-nine of 62 recruited infants completed the study. Maternal temperature, delivery room temperature, transfer-incubator temperature, and time to admission were recorded. Use of occlusive wrapping resulted in a significantly higher admission rectal temperature in infants <28 weeks' gestation (difference in means = 1.9 C, P <.001). No significant difference was seen in admission rectal temperature in infants of 28 to 31 weeks' gestation (difference in means = 0.17 C, P =.47). All 5 deaths were in the nonwrap group (vs wrap, P =.04); their mean temperature was 35.1 C versus 36.5 C in survivors (P =.001).

CONCLUSIONS

Occlusive wrapping of very low birth weight infants at delivery reduces postnatal temperature fall. This may result in a decreased mortality rate.

Biphasic modulation of intracellular Ca2+ concentration by interleukin-1beta in cortical synaptosomes: involvement of a pertussis toxin-sensitive G-protein and mitogen-activated protein kinase

The modulation of intracellular Ca2+ concentration ([Ca2+]i) by the pro-inflammatory cytokine interleukin-1beta (IL-1beta) was assessed in synaptosomes loaded with the Ca2+-sensitive dye, Fura-2AM. IL-1beta was found to exert a biphasic effect on the KCl-induced rise in [Ca2+]i, extending an inhibitory effect at lower (3.5 ng/ml) concentrations, and a stimulatory effect at high (100 ng/ml) concentrations. The inhibitory action of IL-1beta on [Ca2+]i was sensitive to pertussis toxin (PTX; 2 microg/ml), indicating a role for a PTX-sensitive G-protein, but was unaffected by the p42 mitogen-activated protein kinase kinase (MAP kinase kinase) inhibitor, PD 098059 (2 microM). In contrast, the stimulatory action of higher concentrations of IL-1beta on [Ca2+]i was blocked by PD 098059 and unaffected by PTX. We conclude that the biphasic actions of IL-1beta on the KCl-induced rise in [Ca2+]i are mediated through activation of alternative second messenger pathways.

Voltage-dependent binding and calcium channel current inhibition by an anti-alpha 1D subunit antibody in rat dorsal root ganglion neurones and guinea-pig myocytes

1. The presence of calcium channel alpha 1D subunit mRNA in cultured rat dorsal root ganglion (DRG) neurones and guinea-pig cardiac myocytes was demonstrated using the reverse transcriptase-polymerase chain reaction. 2. An antipeptide antibody targeted at a region of the voltage-dependent calcium channel alpha 1D subunit C-terminal to the pore-forming SS1-SS2 loop in domain IV (amino acids 1417-1434) only bound to this exofacial epitope if the DRG neurones and cardiac myocytes were depolarized with 30 mM K+. 3. Incubation of cells under depolarizing conditions for 2-4 h with the antibody resulted in a maximal inhibition of inward current density of 49% (P < 0.005) for DRGs and 30% (P < 0.05) for cardiac myocytes when compared with controls. 4. S-(-)-Bay K 8644 (1 microM) enhanced calcium channel currents in DRGs by 75 +/- 19% (n = 5) in neurones incubated under depolarizing conditions with antibody that had been preabsorbed with its immunizing peptide (100 micrograms ml-1). This was significantly (P < 0.05) larger than the enhancement by S-(-)-Bay K 8644 that was seen with cells incubated under identical conditions but with antibody alone, which was 15 +/- 4% (n = 5). 5. These results demonstrate the presence of calcium channel alpha 1D subunits in rat DRG neurones and guinea-pig cardiac myocytes. They also show that amino acids 1417-1434 of the alpha 1D subunit are only exposed to the extracellular face of the membrane following depolarization and that the binding of an antibody to these amino acids attenuates calcium channel current and reduces the ability of S-(-)-Bay K 8644 to enhance this current, indicating that it is an L-type current that is attenuated.

Importance of the different beta subunits in the membrane expression of the alpha1A and alpha2 calcium channel subunits: studies using a depolarization-sensitive alpha1A antibody

The plasma membrane expression of the rat brain calcium channel subunits alpha1A, alpha2-delta and the beta subunits beta1b, beta2a, beta3b and beta4 was examined by transient expression in COS-7 cells. Neither alpha1A nor alpha2-delta localized to the plasma membrane, either alone or when coexpressed. However, coexpression of alpha1A or alpha2-delta/alpha1A with any of the beta subunits caused alpha1A and alpha2 to be targetted to the plasma membrane. The alpha1A antibody is directed against an exofacial epitope at the mouth of the pore, which is not exposed unless cells are depolarized, both for native alpha1A channels in dorsal root ganglion neurons and for alpha1A expressed with a beta subunit. This subsidiary result provides evidence that either channel opening or inactivation causes a conformational change at the mouth of the pore of alpha1A. Immunostaining for alpha1A was obtained in depolarized non-permeabilized cells, indicating correct orientation in the membrane only when it was coexpressed with a beta subunit. In contrast, beta1b and beta2a were associated with the plasma membrane when expressed alone. However, this is not a prerequisite to target alpha1A to the membrane since beta3 and beta4 alone showed no differential localization, but did direct the translocation of alpha1A to the plasma membrane, suggesting a chaperone role for the beta subunits.