The effect of the enkephalin DADLE on transcription does not depend on opioid receptors

Embedding cell monolayers to investigate nanoparticle-plasmalemma interactions at transmission electron microscopy

Transmission electron microscopy is the technique of choice to visualize the spatial relationships between nanoconstructs and cells and especially to monitor the uptake process of nanomaterials. It is therefore crucial that the cell surface be preserved in its integrity, to obtain reliable ultrastructural evidence: the plasmalemma represents the biological barrier the nanomaterials have to cross, and the mode of membrane-nanoconstruct interaction is responsible for the intracellular fate of the nanomaterials. In this paper, we describe a simple and inexpensive method to process cell monolayers for ultrastructural morphology and immunocytochemistry, ensuring consistent preservation of the cell surface and of the occurring interactions with nanoparticles of different chemical composition.

Synthetic torpor: A method for safely and practically transporting experimental animals aboard spaceflight missions to deep space

Animal research aboard the Space Shuttle and International Space Station has provided vital information on the physiological, cellular, and molecular effects of spaceflight. The relevance of this information to human spaceflight is enhanced when it is coupled with information gleaned from human-based research. As NASA and other space agencies initiate plans for human exploration missions beyond low Earth orbit (LEO), incorporating animal research into these missions is vitally important to understanding the biological impacts of deep space. However, new technologies will be required to integrate experimental animals into spacecraft design and transport them beyond LEO in a safe and practical way. In this communication, we propose the use of metabolic control technologies to reversibly depress the metabolic rates of experimental animals while in transit aboard the spacecraft. Compared to holding experimental animals in active metabolic states, the advantages of artificially inducing regulated, depressed metabolic states (called synthetic torpor) include significantly reduced mass, volume, and power requirements within the spacecraft owing to reduced life support requirements, and mitigated radiation- and microgravity-induced negative health effects on the animals owing to intrinsic physiological properties of torpor. In addition to directly benefitting animal research, synthetic torpor-inducing systems will also serve as test beds for systems that may eventually hold human crewmembers in similar metabolic states on long-duration missions. The technologies for inducing synthetic torpor, which we discuss, are at relatively early stages of development, but there is ample evidence to show that this is a viable idea and one with very real benefits to spaceflight programs. The increasingly ambitious goals of world's many spaceflight programs will be most quickly and safely achieved with the help of animal research systems transported beyond LEO; synthetic torpor may enable this to be done as practically and inexpensively as possible.

Delta Opioid Receptor and Peptide: A Dynamic Therapy for Stroke and Other Neurological Disorders

Research of the opioid system and its composite receptors and ligands has revealed its promise as a potential therapy for neurodegenerative diseases such as stroke and Parkinson's Disease. In particular, delta opioid receptors (DORs) have been elucidated as a therapeutically distinguished subset of opioid receptors and a compelling target for novel intervention techniques. Research is progressively shedding light on the underlying mechanism of DORs and has revealed two mechanisms of DOR neuroprotection; DORs function to maintain ionic homeostasis and also to trigger endogenous neuroprotective pathways. Delta opioid agonists such as (D-Ala2, D-Leu5) enkephalin (DADLE) have been shown to promote neuronal survival and decrease apoptosis, resulting in a substantial amount of research for its application as a neurological therapeutic. Most notably, DADLE has demonstrated significant potential to reduce cell death following ischemic events. Current research is working to reveal the complex mechanisms of DADLE's neuroprotective properties. Ultimately, our knowledge of the DOR receptors and agonists has made the opioid system a promising target for therapeutic intervention in many neurological disorders.

Organ protective mechanisms common to extremes of physiology: a window through hibernation biology

Supply and demand relationships govern survival of animals in the wild and are also key determinants of clinical outcomes in critically ill patients. Most animals' survival strategies focus on the supply side of the equation by pursuing territory and resources, but hibernators are able to anticipate declining availability of nutrients by reducing their energetic needs through the seasonal use of torpor, a reversible state of suppressed metabolic demand and decreased body temperature. Similarly, in clinical medicine the majority of therapeutic interventions to care for critically ill or trauma patients remain focused on elevating physiologic supply above critical thresholds by increasing the main determinants of delivery of oxygen to the tissues (cardiac output, perfusion pressure, hemoglobin concentrations, and oxygen saturation), as well as increasing nutritional support, maintaining euthermia, and other general supportive measures. Techniques, such as induced hypothermia and preconditioning, aimed at diminishing a patient's physiologic requirements as a short-term strategy to match reduced supply and to stabilize their condition, are few and underutilized in clinical settings. Consequently, comparative approaches to understand the mechanistic adaptations that suppress metabolic demand and alter metabolic use of fuel as well as the application of concepts gleaned from studies of hibernation, to the care of critically ill and injured patients could create novel opportunities to improve outcomes in intensive care and perioperative medicine.

[D-Ala2, D-Leu5] encephalin (DADLE) reversibly inhibits cellular transcription in neurons without causing cell injury

[d-Ala(2)-d-Leu(5)]-Enkephalin (DADLE) has shown promising results in protecting neurons from damages. However, the mechanism for this protection is still under investigation. The current study was carried out to test the hypothesis that DADLE may regulate cellular transcription in neurons. SH-SY5Y cells and primary cortical neurons were treated with various doses of DADLE for 24-72h. Results demonstrated that DADLE, at all doses and time points examined, significantly inhibited cellular transcription in both cells without causing cell injury. Following recovery for 72h without DADLE in primary neurons, the transcriptional activity fully resumed. Delta opioid receptor (DOR) is not involved in this process, as Naltrindole could not abolish DADLE׳s transcriptional inhibitory effects. Further studies in primary cortical neurons show that DADLE significantly inhibited phosphorylation of Ser2 and Ser5 of the C-terminal domain (CTD) of RNA polymerase II. These data indicate that DADLE is able to decrease cellular transcription through inhibiting phosphorylation of RNA polymerase II in neurons, which may provide mechanistic insight into its reported neuroprotective effects, and suggests that it warrants further exploration as a potential therapeutic strategy for neuroprotection.

Induction of torpor: mimicking natural metabolic suppression for biomedical applications

Mammalian hibernation consists of periods of depressed metabolism and reduced body temperature called "torpor" that are interspersed by normothermic arousal periods. Numerous cellular processes are halted during torpor, including transcription, translation, and ion homeostasis. Hibernators are able to survive long periods of low blood flow and body temperature followed by rewarming and reperfusion without overt signs of organ injury, which makes these animals excellent models for application of natural protective mechanisms to human medicine. This review examines efforts to induce torpor-like states in non-hibernating species using pharmacological compounds. Elucidating the underlying mechanisms of natural and pharmacologically induced torpor will speed the development of new clinical approaches to treat a variety of trauma and stress states in humans.

Transport of the synthetic opioid peptide DADLE ([D-Ala2,D-Leu5]-enkephalin) in neuronal cells

The sodium-coupled oligopeptide transporters 1 and 2 (SOPT1 and SOPT2) transport peptides consisting of at least five amino acids and show potential for the delivery of therapeutically relevant peptides/peptidomimetics. Here, we examined the expression of these two transporters in the retinal neuronal cell line RGC-5. These cells showed robust uptake activity for the synthetic pentapeptide DADLE ([D-Ala(2),D-Leu(5)]-Enkephalin). The uptake was Na(+) dependent and saturable (K(t), 6.2 ± 0.6 μM). A variety of oligopeptides inhibited DADLE uptake. The uptake of the competing oligopeptides was directly demonstrated with fluorescein isothiocyanate-labeled Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys in RGC-5 cells and primary mouse retinal ganglion cells. The characteristics of DADLE uptake matched those of SOPT2. We then examined the expression of SOPT1 in these cells with deltorphin II (Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH(2)) as the substrate and found that RGC-5 cells also expressed SOPT1. As it is already known that SOPT1 is expressed in the neuronal cell line SK-N-SH, we investigated SOPT2 expression in these cells to determine whether the presence of both oligopeptide transporters is a common feature of neuronal cells. These studies showed that SK-N-SH cells also expressed SOPT2. This constitutes the first report on the functional characterization of SOPT1 and SOPT2 in retinal neuronal cells and on the expression of SOPT2 in nonretinal neuronal cells.

Induction of an in vitro reversible hypometabolism through chitosan-based nanoparticles

OBJECTIVE

Chitosan-based nanoparticles (NPs) were prepared to promote intracellular sustained delivery of the synthetic delta opioid D-Ala(2)-D-Leu(5)-enkephalin (DADLE), prolonging peptide activity and inducing a safe and reversible hypometabolic state.

MATERIALS AND METHODS

NPs were prepared by combining ionotropic gelation and ultrasonication treatment. NP uptake studies and the effects of encapsulated DADLE on HeLa cells proliferation were tested by transmission electron microscopy (TEM) analysis, by immuno-fluorescence and immuno-cytochemistry.

RESULTS

DADLE-loaded NPs are produced with suitable characteristics, a satisfactory process yield (55.4% ± 2.4%) and encapsulation efficiency (64.6% ± 2.1%). NPs are effective in inducing a hypometabolic stasis at a 10(-4) M DADLE concentration. Moreover, as seen from the immunofluorescence study, the effect persists through the recovery period (72 h). Indeed, NPs labelled by anti-enkephalin antibody inside cell nucleus reassert that the in vivo release of the peptide can be prolonged with respect to the case of free peptide supply.

CONCLUSION

The nanoparticulate drug delivery system described seems to be effective in inducing and prolonging a sort of hibernation-like state in the cells.

Delta opioid peptide [D-Ala2, D-Leu5] enkephalin (DADLE) triggers postconditioning against transient forebrain ischemia

Preconditioning with selective delta opioid peptide [d-Ala2, d-Leu5] enkephalin (DADLE) provides ischemic tolerance following transient forebrain ischemia in rats. However, whether DADLE postconditioning retains its neuroprotective efficacy and the underlying molecular mechanism in ischemic brain is largely unknown. We investigated DADLE postconditioning protection of hippocampal CA1 neurons against transient forebrain ischemia. 6 days after being implanted with cannula at the right lateral ventricle, rats underwent 10 min of forebrain ischemia by four vessel occlusion. Hippocampal CA1 neuronal survival and degeneration were measured in the hippocampi of rats at 3 days after ischemia. The behavioral and cognitive improvements of DADLE treatment in rats were also evaluated on days 5-9 using open-field and Morris water maze tests. The results showed that DADLE at doses of 0.25 and 2.5 nmol, but not 25 nmol, could significantly protect CA1 neurons against ischemia/reperfusion injury. Co-administration with the delta-opioid receptor antagonist naltrindole or pretreatment with the Akt antagonist LY294002 completely abolished the DADLE postconditioning effect. Furthermore, DADLE postconditioning exhibited cognitive benefits in rats with transient forebrain ischemia. The study thus suggested a therapeutic opportunity of postconditioning neuroprotection by DADLE and also provided important information in understanding the mechanism of DADLE action in the ischemic brain.

Signal transduction pathways involved in brain death-induced renal injury

Kidneys derived from brain death organ donors show an inferior survival when compared to kidneys derived from living donors. Brain death is known to induce organ injury by evoking an inflammatory response in the donor. Neuronal injury triggers an inflammatory response in the brain, leading to endothelial dysfunction and the release of cytokines in the circulation. Serum levels of interleukin-6, -8, -10, and monocyte chemoattractant protein-1 (MCP-1) are increased after brain death. Binding with cytokine-receptors in kidneys stimulates activation of nuclear factor-kappa B (NF-kappaB), selectins, adhesion molecules and production of chemokines leading to cellular influx. Mitogen-activated protein kinases (MAP-kinases) mediate inflammatory responses and together with NF-kappaB they seem to play an important role in brain death induced renal injury. Altering the activation state of MAP-kinases could be a promising drug target for early intervention to reduce cerebral injury related donor kidney damage and improve outcome after transplantation.

Selective distribution of protein kinase A regulatory subunit RII{alpha} in rodent gliomas

Differential diagnosis of brain tumor types is mainly based on cell morphology and could benefit from additional markers. The cAMP second-messenger system is involved in regulating cell proliferation and differentiation and is conceivably modulated during cancer transformation. The cAMP second-messenger system mainly activates protein kinases, which are in part docked to cytoskeleton, membranes, or organelles by anchoring proteins, forming protein aggregates that are detergent insoluble and not freely diffusible and that are characteristic for each cell type. The intracellular distribution of the detergent-insoluble regulatory subunits (R) of the cAMP-dependent protein kinase has been examined in mouse and rat glioma cells both in vitro and in vivo by immunohistochemistry. In normal rodent brains, the RIIalpha regulatory subunit is detergent insoluble only in ependymal cells, while in the rest of the brain it is present in soluble form. Immunohistochemistry shows that in both mouse and rat glioma cell lines, RIIalpha is mainly detergent insoluble. RIIalpha is localized close to the nucleus, associated with smooth vesicles in the trans-Golgi network area. Both paclitaxel and vinblastine cause a redistribution of RIIalpha within the cell. Under conditions that increased intracellular cAMP, apoptosis of glioma cells was observed, and it was accompanied by RIIalpha redistribution. Also in vivo, detergent-insoluble RIIalpha can be observed in mouse and rat gliomas, where it delineates the border between normal brain tissue and glioma. Therefore, intracellular distribution of detergent-insoluble RIIalpha can assist in detecting tumor cells within the brain, thus making the histologic diagnosis of brain tumors more accurate, and may represent an additional target for therapy.

Perichromatin fibrils as early markers of transcriptional alterations

Perichromatin fibrils represent the morphological expression of transcription and co-transcriptional processing of pre-mRNA. They can be considered, hence, an example of work in progress. High resolution techniques such as electron microscopy demonstrate that perichromatin fibrils play a role as early markers of transcriptional alterations. In this paper, we review some experimental and physiological conditions impairing or modulating transcription as well as their effects on perichromatin fibrils. In all the situations reported, perichromatin fibrils show modifications in their amount and/or their associated proteins. Their movements are also affected, as well as their export or their intra-nuclear storage forms. Perichromatin fibrils therefore represent highly sensitive markers not only for monitoring transcriptional and processing rate but also for identifying the maturation level of pre-mRNA/mRNA occurring in the cell nucleus and the functional correlation with the cellular metabolic state.

Variation in the analgesic activity of opioid peptide fragments in correlation with the amino acidic sequence

Short fragments of typical or atypical opioid peptides, lacking the whole four amino acid sequence of the enkephalin motif, can preserve a significant percentage of the analgesic activity of the original peptides. This paper investigates the importance of the amino-acidic sequence of minimum structure typical opioid peptides for the analgesic activity. Different groups of rats were treated with 1) Gly-Tyr, 0.5 mg/rat i.t., 2) Tyr-Gly, 0.5 mg/rat i.t., 3) Tyr-Gly-Gly, 0.5 mg/rat i.t., 4) Gly-Gly-Phe-Leu, 0.5 mg/rat i.t., 5) Leu-enkephalin, 0.5 mg/rat i.t.. The analgesic effect of the tested substances was appreciated through the nociceptive threshold for thermal (plantar test) and mechanical nociception (algesimetric test). Fragments of typical opioid peptides elicited antinociceptive activity only when a tyrosine residue was present at the N-terminal end of the amino-acidic sequence. The presence of Nterminal tyrosine provides affinity for the opioid receptors and significant analgesic activity. The intensity of the antinociceptive effect was directly proportional with the length of the amino-acidic sequence. The inhibition of the analgesic effect by previous administration of naloxone proves that this effect is mediated through the opioid system.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

The histochemistry and cell biology vade mecum: a review of 2005–2006

The procurement of new knowledge and understanding in the ever expanding discipline of cell biology continues to advance at a breakneck pace. The progress in discerning the physiology of cells and tissues in health and disease has been driven to a large extent by the continued development of new probes and imaging techniques. The recent introduction of semi-conductor quantum dots as stable, specific markers for both fluorescence light microscopy and electron microscopy, as well as a virtual treasure-trove of new fluorescent proteins, has in conjunction with newly introduced spectral imaging systems, opened vistas into the seemingly unlimited possibilities for experimental design. Although it oftentimes proves difficult to predict what the future will hold with respect to advances in disciplines such as cell biology and histochemistry, it is facile to look back on what has already occurred. In this spirit, this review will highlight some advancements made in these areas in the past 2 years.